(X+1) (X+2) (X+3) (X+4) = 120
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Posted by Nitesh Ganjhu 4 years, 9 months ago
- 2 answers
Yogita Ingle 4 years, 9 months ago
Rewrite the equation as:
(x + 1)(x + 4)(x + 3)(x + 2) = 120
Multiply the first 2 and last 2 expressions:
{tex}(x^2 + 5x + 4)(x^2 + 5x + 6) = 120{/tex} ..... (1)
Let {tex}x^2 + 5x = y{/tex}
(1) becomes,
(y + 4)(y + 6) = 120
y2 + 10x + 24 = 120
y2 + 10x - 96 = 0
y2 + 16x - 6y - 96 = 0
y(y + 16) - 6(y + 16) = 0
(y + 16)(y - 6) = 0
y = -16 or 6
y2+ 5x = 16 or 6
When x2 + 5x = 6
x2 + 5x - 6 = 0
x2 + 6x - x - 6 = 0
x(x + 6) - 1(x + 6) = 0
(x + 6)(x - 1) = 0
x = -6, 1
When x^2 + 5x = -16
x^2 + 5x + 16 = 0
Using quadratic formula:
{tex}x = [-5 +/- sqrt (25 - 64)]/2{/tex}
The solutions are, -6, 1, [-5 - sqrt (25 - 64)]/2 and [-5 + sqrt (25 - 64)]/2
These are all the possible solutions. But the only real solutions are -6 and 1.
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Rajneesh Payal 4 years, 9 months ago
0Thank You