Question

solve for x
(x+1)(x+3)(x+5)(x+7) = 1920

Answer 1

(x+1)(x+3)(x+5)(x+7) = 1920
(x^2 + 4x + 3)(x^2 + 12x + 35) = 1920
x^4 + 12x^3 + 4x^3 + 35x^2 + 3x^2 + 48x^2 + 140x + 36x + 105 = 1920
x^4 + 16x^3 + 86x^2 + 176x - 1815 = 0

Answer 2

what ? so what's the answer then ...
please teach me

Answer 3

The answer is in the screenshots. x = 3 or x = -11 (if you don't consider complex no)

Answer 4

x=3,−11,−4+i√39,−4−i√39

Answer 5

ah, sorry forgot to saying that the x must be positive integer.
hmmm, what method is it ?