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Solve `(x^(2) - 2x)^(2) - 23 (x^(2) - 2x) + 120 = 0` |
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Answer» Let us assume that `x^(2) - 2x = y` `rArr` The given equation reduced to a quadratic equation in y. That is, `y^(2)- 23 + 120 = 0` `rArr y^(2) - 15y - 8y + 120 = 0` `rArr y(y-15) - 8 (y-5) = 0` `rArr (y-8) (y-15) = 0` `rArr y - 8 = 0` (or) `y - 15 = 0` `rArr y = 8`(or) `y = 15` But `x^(2) - 2x = y` When `y = 8, x^(2) - 2x = 8` When `y = 8, x^(2)- 2x = 8` `rArr x^(2) - 2x - 8 = 0` `rArr x^(2) - 4x + 2x - 8 = 0` `rArr x(x-4) +2(x-4) = 0` `rArr (x+2) (x-4) = 0` `rArr x+2 = ` (or) `x - 4 = 0` `rArr x = - 2` (or) `x = 4` When `y = 15, x^(2)- 2x = 15` `rArr x^(2) - 2x - 15 = 0` `rArr x^(2)- 5x + 3x - 15 = 0` `rArr x(x-5) + 3(x-5) = 0` `rArr (x-5) (x+3)= 0` `rArr x- 5 = 0` (or) `x + 3 = 0` `rArr x= 5` (or) `x =-3` `:. x = - 2,-3, 4` and 5 are the required solutions of the given equation . |
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