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What work is involved in solving the equation x=3x*√(-6x+10)?

 Nov 4, 2015
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Solve for x:
x = 3 x sqrt(10-6 x)

Subtract 3 x sqrt(10-6 x) from both sides:
x-3 x sqrt(10-6 x) = 0

Simplify and substitute y = sqrt(10-6 x):
x-3 sqrt(10-6 x) x  =  5/3-5 sqrt(10-6 x)-(sqrt(10-6 x)^2)/(6)+sqrt(10-6 x)^3/2  =  y^3/2-y^2/6-5 y+5/3  =  0:
y^3/2-y^2/6-5 y+5/3 = 0

The left hand side factors into a product with three terms:
1/6 (3 y-1) (y^2-10) = 0

Multiply both sides by 6:
(3 y-1) (y^2-10) = 0

Split into two equations:
3 y-1 = 0 or y^2-10 = 0

Add 1 to both sides:
3 y = 1 or y^2-10 = 0

Divide both sides by 3:
y = 1/3 or y^2-10 = 0

Substitute back for y = sqrt(10-6 x):
sqrt(10-6 x) = 1/3 or y^2-10 = 0

Raise both sides to the power of two:
10-6 x = 1/9 or y^2-10 = 0

Subtract 10 from both sides:
-6 x = -89/9 or y^2-10 = 0

Divide both sides by -6:
x = 89/54 or y^2-10 = 0

Add 10 to both sides:
x = 89/54 or y^2 = 10

Take the square root of both sides:
x = 89/54 or y = sqrt(10) or y = -sqrt(10)

Substitute back for y = sqrt(10-6 x):
x = 89/54 or sqrt(10-6 x) = sqrt(10) or y = -sqrt(10)

Raise both sides to the power of two:
x = 89/54 or 10-6 x = 10 or y = -sqrt(10)

Subtract 10 from both sides:
x = 89/54 or -6 x = 0 or y = -sqrt(10)

Divide both sides by -6:
x = 89/54 or x = 0 or y = -sqrt(10)

Substitute back for y = sqrt(10-6 x):
x = 89/54 or x = 0 or sqrt(10-6 x) = -sqrt(10)

Raise both sides to the power of two:
x = 89/54 or x = 0 or 10-6 x = 10

Subtract 10 from both sides:
x = 89/54 or x = 0 or -6 x = 0

Divide both sides by -6:
Answer: | 
| x = 89/54                   or x = 0

 Nov 4, 2015

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