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how would I (if it's possible) factor: 8x^3-12x^2-2x=0 to find values of x

 Dec 8, 2015
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Solve for x:
8 x^3-12 x^2-2 x = 0

Factor x and constant terms from the left hand side:
2 x (4 x^2-6 x-1) = 0

Divide both sides by 2:
x (4 x^2-6 x-1) = 0

Split into two equations:
x = 0 or 4 x^2-6 x-1 = 0

Divide both sides by 4:
x = 0 or x^2-(3 x)/2-1/4 = 0

Add 1/4 to both sides:
x = 0 or x^2-(3 x)/2 = 1/4

Add 9/16 to both sides:
x = 0 or x^2-(3 x)/2+9/16 = 13/16

Write the left hand side as a square:
x = 0 or (x-3/4)^2 = 13/16

Take the square root of both sides:
x = 0 or x-3/4 = sqrt(13)/4 or x-3/4 = -sqrt(13)/4

Add 3/4 to both sides:
x = 0 or x = 3/4+sqrt(13)/4 or x-3/4 = -sqrt(13)/4

Add 3/4 to both sides:
Answer: |   x = 0     or x = 3/4+sqrt(13)/4    or x = 3/4-sqrt(13)/4
 

 Dec 8, 2015

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