An algebra problem by Daehan Lee

Algebra Level 1

x 2 + x + 6 = 62 \large x^2+x+6 = 62

Find the positive value of x x satisfying the equation above.

12 11 6 7 3 9

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2 solutions

Ashish Menon
May 27, 2016

x 2 + x + 6 = 62 x 2 + x + 6 62 = 0 x 2 + x 56 = 0 x 2 + ( 8 x 7 x ) 56 = 0 ( x 2 + 8 x ) ( 7 x + 56 ) = 0 x ( x + 8 ) 7 ( x + 8 ) = 0 ( x + 8 ) ( x 7 ) = 0 \begin{aligned} x^2 + x + 6 & = 62\\ x^2 + x + 6 - 62 & = 0\\ x^2 + x - 56 & = 0\\ x^2 + \left(8x - 7x\right) - 56 & = 0\\ \left(x^2 + 8x\right) - \left(7x + 56\right) & = 0\\ x\left(x + 8\right) - 7\left(x + 8\right) & = 0\\ \left(x + 8\right)\left(x - 7\right) & = 0 \end{aligned}

( x + 8 ) = 0 ( or ) ( x 7 ) = 0 x = 8 ( or ) x = 7 \begin{aligned} \left(x + 8\right) = 0 & \left(\text{or}\right) & \left(x - 7\right) = 0\\ x = -8 & \left(\text{or}\right) & x = 7 \end{aligned}

So, the positive value of x x satisfying the given equation = 7 \color{#69047E}{\boxed{7}} .

Daehan Lee
May 27, 2016

First subtract 6 6 from both side. That gives us x 2 + x = 56 x^2+x=56 . And x 2 + x = 56 x^2+x=56 . So 7 2 + 7 = 56 7^2+7=56

Thanks for sharing this problem, Daehan. :)

Pranshu Gaba - 5 years ago

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:V Ha ha ha :p

Rezwan Arefin - 5 years ago

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