6.5 – Solving Equations w/ Rational Expressions
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Transcript of 6.5 – Solving Equations w/ Rational Expressions
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6.5 – Solving Equations w/ Rational Expressions
5 16 1x 4 14 5 20x
4 14 5
20 2020
20x
5x
LCD: 20
5 16 1x
5 15x
3x
44 11
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LCD:
2 3 3 3 2x x 2
2 3 23 3 9x x x
2 3 2
3 3 3 3x x x x
3 3x x
3 3 23x
x x
2 3 3 3 2x x
2 6 3 9 2x x
5 3 2x
5 5x 1x
3 33
3x
x x
3
3 33 2x x
x x
6.5 – Solving Equations w/ Rational Expressions
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LCD: 6x5 3 33 2 2x
6 53
x
2 5 3 3 3 3x x 10 9 9x x
9x
362x
x 2
6 3x
10 9 9x x
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LCD: x+36 2 23 3
xxx x
3x x
2 3x x
2 12 0x x 3x
3 0 4 0x x 3x
3 63x
x
233
x xx
3 2x
6 2x 2 6x 2 3x x 6 4 6x
0 4x 4x
6.5 – Solving Equations w/ Rational Expressions
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LCD:
2
5 11 1 122 7 10 5
xx x x x
5 11 1 12
2 2 5 5x
x x x x
2 5x x
2 5 52x
x x
5 5 11 1 12 2x x x
5 25 11 1 12 24x x x
5 25 23x x
6 48x 8x
12 5
2 1 15 xx
xx
x
2 5 12
5x
xx
6.5 – Solving Equations w/ Rational Expressions
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LCD: abx1 1 1a b x
1abxa
bx
bx ab ax
bx
bxb x
Solve for a
1b
abx 1x
abx
ax ab
a b x
a
6.5 – Solving Equations w/ Rational Expressions
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Problems about NumbersIf one more than three times a number is divided by the number, the result is four thirds. Find the number.
3x
3 3 1x xx
3 3 1 4x x
9 3 4x x
5 3x 35
x
LCD = 3x1x
43
3
3 4x
9 4 3x x
6.6 – Rational Equations and Problem Solving
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Problems about Work Mike and Ryan work at a recycling plant. Ryan can sort a batch of recyclables in 2 hours and Mike can sort a batch in 3 hours. If they work together, how fast can they sort one batch?
Time to sort one batch (hours)
Fraction of the job completed in one hour
Ryan
Mike
Together
12131x
2
3
x
6.6 – Rational Equations and Problem Solving
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Problems about Work Time to sort
one batch (hours)
Fraction of the job completed in one hour
Ryan
Mike
Together
12131x
2
3
x
12 6 1
2x
3x 5 6x 65
x hrs.
LCD =13
1x
6x 3
6 1x 16x
x
2x 6115
6.6 – Rational Equations and Problem Solving
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James and Andy mow lawns. It takes James 2 hours to mow an acre while it takes Andy 8 hours. How long will it take them to mow one acre if they work together?
Time to mow one acre (hours)
Fraction of the job completed in one hour
James
Andy
Together
2
8
x
12181x
6.6 – Rational Equations and Problem Solving
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Time to mow one acre (hours)
Fraction of the job completed in one hour
James
Andy
Together
2
8
x
12181x
LCD:12
8 12
x
4x 5 8x 85
x
hrs.
18
1x
8x 8
8 1x 18x
x
x 8315
6.6 – Rational Equations and Problem Solving
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A sump pump can pump water out of a basement in twelve hours. If a second pump is added, the job would only take six and two-thirds hours. How long would it take the second pump to do the job alone?
112
1x
263
1203
Time to pump one basement (hours)
Fraction of the job completed in one hour
1st pump
2nd pump
Together
x
12
203
6.6 – Rational Equations and Problem Solving
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112
1x
263
1203
Time to pump one basement (hours)
Fraction of the job completed in one hour
1st pump
2nd pump
Together
x
12
112
1 112 x
203
1x
1203
320
6.6 – Rational Equations and Problem Solving
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LCD:
60 112
x
5x
60 4xhrs. 15x
1 1 312 20x
60x
160x
x 0
60 32
x
60 9x
5x60 9x
6.6 – Rational Equations and Problem Solving
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Distance, Rate and Time Problems If you drive at a constant speed of 65 miles per hour and you travel for 2 hours, how far did you drive?
d r t
65mileshour
2 hours 130 miles
d tr
d rt
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A car travels six hundred miles in the same time a motorcycle travels four hundred and fifty miles. If the car’s speed is fifteen miles per hour faster than the motorcycle’s, find the speed of both vehicles.
Rate Time Distance
Motor-cycle
Car
x
x + 15
450 mi
600 mi
t
t
rdt
x450
15600x
6.6 – Rational Equations and Problem Solving
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Rate Time Distance
Motor-cycle
Car
x
x + 15
450 mi
600 mi
t
t
rdt
x450
15600x
x450
15
600x
LCD: x(x + 15)
15600450
xx
x(x + 15) x(x + 15)
6.6 – Rational Equations and Problem Solving
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15600450
xx
x(x + 15) x(x + 15)
xx 60045015
xx 60015450450
x15015450
x
15015450
x45
45x mphMotorcycle
6015 x mphCar
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Rate Time Distance
UpStream
DownStream
A boat can travel twenty-two miles upstream in the same amount of time it can travel forty-two miles downstream. The speed of the current is five miles per hour. What is the speed of the boat in still water? boat speed = x
x - 5
x + 5
22 mi
42 mi
t
t
rdt
522x
542x
6.6 – Rational Equations and Problem Solving
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Rate Time Distance
UpStream
DownStream
boat speed = x
x - 5
x + 5
22 mi
42 mi
t
t
rdt
522x
542x
522x
5
42x
LCD: (x – 5)(x + 5)
542
522
xx(x – 5)(x + 5) (x – 5)(x + 5)
6.6 – Rational Equations and Problem Solving
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542225 xx
2104211022 xx
xx 2242210110
x20
320
x1616 mph
Boat Speed
542
522
xx(x – 5)(x + 5) (x – 5)(x + 5)
x20320
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Direct Variation: y varies directly as x (y is directly proportional to x), if there is a nonzero constant k such that
6.7 – Variation and Problem Solving
The number k is called the constant of variation or the constant of proportionality
.kxy
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Direct Variation
kxy 824 k
k824
6.7 – Variation and Problem Solving
Suppose y varies directly as x. If y is 24 when x is 8, find the constant of variation (k) and the direct variation equation.
3k
xy 3direct variation equation
constant of variation
xy
39
515
927
1339
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kwd 567 k
k567
6.7 – Variation and Problem SolvingHooke’s law states that the distance a spring stretches is directly proportional to the weight attached to the spring. If a 56-pound weight stretches a spring 7 inches, find the distance that an 85-pound weight stretches the spring. Round to tenths.
81
k
xy31
direct variation equation
constant of variation
8531
y
6.10y inches
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Inverse Variation: y varies inversely as x (y is inversely proportional to x), if there is a nonzero constant k such that
6.7 – Variation and Problem Solving
The number k is called the constant of variation or the constant of proportionality.
.xk
y
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Inverse Variation
xk
y
36
k
k18
6.7 – Variation and Problem Solving
Suppose y varies inversely as x. If y is 6 when x is 3, find the constant of variation (k) and the inverse variation equation.
xy
18
direct variation equation
constant of variation
xy
36
92
101.8
181
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tk
r
430
k
k120
6.7 – Variation and Problem SolvingThe speed r at which one needs to drive in order to travel a constant distance is inversely proportional to the time t. A fixed distance can be driven in 4 hours at a rate of 30 mph. Find the rate needed to drive the same distance in 5 hours.
xr
120
direct variation equation
constant of variation
5120
r
24r mph
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Joint Variation6.7 – Variation and Problem Solving
If the ratio of a variable y to the product of two or more variables is constant, then y varies jointly as, or is jointly proportional, to the other variables.Therefore, if , then the number k is the constant of variation or the constant of proportionality.
𝑧=𝑘𝑥𝑦
z varies jointly as x and y. x = 3 and y = 2 when z = 12. Find z when x = 4 and y = 5.
12=𝑘 (3 ) (2 ) 2=𝑘 𝑧=2 𝑥𝑦𝑧=2 (4 ) (5 ) 𝑧=40
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Joint Variation6.7 – Variation and Problem Solving
𝑉=𝑘h𝑟 2
V varies jointly as h and . V = 402.12 cubic inches, h = 8 inches and r = 4 inches. Find V when h = 10 and r = 2.
402.12=𝑘 (8 ) ( 4 )2 3.142=𝑘𝑉=3.142h𝑟 2 𝑖𝑛3𝑉=125.68
The volume of a can varies jointly as the height of the can and the square of its radius. A can with an 8 inch height and 4 inch radius has a volume of 402.12 cubic inches. What is the volume of a can that has a 2 inch radius and a 10 inch height?
𝑉=3.142 (10 )22
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Additional Problems
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LCD: 15
5 2 3 1 1x x 2 1 13 5 15x x
15 152 1 13 5 15
15x x
5 2x
5 10 3 3 1x x
2 13 1x
2 12x
6x 13 x 11
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LCD: x
22 6 7x x x 62 7xx
62 7xx
x x x x
2x
20 5 6x x
1 0 6 0x x
1 6x x
0 1 6x x
6 2x 7x
6.5 – Solving Equations w/ Rational Expressions
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LCD:5 5 31 1x
x x
51
1x xx
5 5 3 3x x
2 2x 1x
1x
1 51x
x
1 3x
5 3 5 3x x
Not a solution as equations is undefined at x = 1.
6.5 – Solving Equations w/ Rational Expressions
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Problems about Numbers
The quotient of a number and 2 minus 1/3 is the quotient of a number and 6. Find the number.
2x
62x
3 2x x 3 2x x
1x
LCD = 613
6x
3
6 1 6
6x
2 2x
6.6 – Rational Equations and Problem Solving
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7.1 – RadicalsRadical Expressions
Finding a root of a number is the inverse operation of raising a number to a power.
This symbol is the radical or the radical sign
n aindex radical sign
radicand
The expression under the radical sign is the radicand.
The index defines the root to be taken.
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Radical Expressions
The symbol represents the negative root of a number.
The above symbol represents the positive or principal root of a number.
7.1 – Radicals
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Square Roots
If a is a positive number, then
a is the positive square root of a and
100
a is the negative square root of a.
A square root of any positive number has two roots – one is positive and the other is negative.
Examples:
10
2549
57
0.81 0.9
36 6
9 non-real #
8x 4x
7.1 – Radicals
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RdicalsCube Roots
3 27
A cube root of any positive number is positive.
Examples:
354
312564
3 8 2
A cube root of any negative number is negative.
3 a
3 3x x 3 12x 4x
7.1 – Radicals
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nth Roots
An nth root of any number a is a number whose nth power is a.
Examples:
2
4 81 3
4 16
5 32 2
43 81
42 16
52 32
7.1 – Radicals
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nth Roots
4 16
An nth root of any number a is a number whose nth power is a.
Examples:
15 1
Non-real number
6 1 Non-real number
3 27 3
7.1 – Radicals
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15023 2 xxxx2
xx 62 2 x6 15
6
186 x
3
33
x
3152 2
xx
6.4 – Synthetic Division
𝑥−3=0𝑥=3
3 −2 0 15
−2−6−6−18−3
−2 𝑥−6− 3𝑥−3
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6.4 – Synthetic Division
2 𝑥−1=0𝑥=1/2
1/2 8 2 −7
8463−4
8 𝑥 +6− 4𝑥−3
12728 2
xxx
12 x
12434x
x
Synthetic division will only work with linear factors with an one as the x-coefficient.