Saturday, April 21, 2012

(x+1) (x+3) (x+4) (x+6) = 72

Find the real root of (x+1) (x+3) (x+4) (x+6) = 72 if any.
(x+1) (x+6) (x+3) (x+4) = 72
(x2+7x+6) (x2+7x+12) = 72

let, x2+7x+6 = g

g (g+6) = 72
g2+6g-72 = 0
(g-6) (g+12) = 0
g = 6, -12

recall, x2+7x+6 = g
x2+7x+6 = 6
x2+7x = 0
x (x+7) = 0
x = 0, -7

g = -12 will give 2 imaginary roots.

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