Underground-X

Algebra Level 1

x(x - 12) = 30 + x(x + 3)

What is the value of x ?


The answer is -2.

Nguyễn Scott by Nguyễn Scott , 21, Canada

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3 solutions

Akash Gupta
Jan 31, 2015

x(x-12)=30+x(x+3)
x^2-12x=30+x^2+3x
x^2-12x-x^2-3x=30
-15x=30
x=30/-15=-2


3 Helpful 0 Interesting 0 Brilliant 0 Confused

x^2 - 12x = 30 + x^2 + 3x now x^2 gets cancelled on both sides and we have ; -12x = 30 +3x i.e. -15x = 30 and x. = -2

2 Helpful 0 Interesting 0 Brilliant 0 Confused

There is a error. It is not 16x, it is 15x Therefore, x=-2 @Karandeep Singh Ludhar

Sudhir Aripirala - 6 years, 4 months ago
Simon Frohlich
Sep 25, 2015

x ( x − 12 ) = 30 + x ( x + 3 ) x(x - 12) = 30 + x(x + 3)

Expand: x 2 − 12 x = 30 + x 2 + 3 x x^2 - 12x = 30 + x^2 + 3x

Combine like terms: − 15 x = 30 -15x = 30

x = − 2 x =\boxed{-2}

1 Helpful 0 Interesting 0 Brilliant 0 Confused

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