Source: Official Guide for the GMAT 13th Ed. Problem Solving; #45 Official Guide for the GMAT 2015 14th Ed. Problem Solving; #45

2

If 4 is one solution of the

If 4 is one solution of the x+3x+k=10, where k is a constant, what is the other solution?

2 Explanations

2

x"2 + 3x + k = 10
x"2 + 3x + (k - 10) = 0

So, being a quadratic equation, we can deduce about the binomial factors:

(X + Y) ( X + Z ) = 0

that:

Y + Z = 3x
and
Y * Z = k - 10

Since one solution is X=4, the binomial factors expression will be:

(X - 4) (X + Z)

Since -4 + Z = 3

Z = 7

So, the binomial expression will be:

(X - 4) (X + 7) = 0

To conclude, the two solutions of the equation will be 4 and -7.

Correct answer (A), (-7)

Jan 25, 2015 • Comment

4

Gravatar Mike McGarry, Magoosh Tutor

Dec 27, 2013 • Comment

Add Your Explanation

You must have a Magoosh account in order to leave an explanation.

Learn More About Magoosh

Official GMAT Material

Official Guide for GMAT Review 2016

Official Guide for the GMAT 2015 14th Ed.

Official Guide for the GMAT 13th Ed.

Nova's GRE Prep

Official Guide for the GMAT 12th Ed.

Revised GRE PDF 2nd Ed.


Section 5.3 Problem Solving

Section 5.3 Problem Solving

Improve Your Score

Magoosh GMAT is an affordable online course for studying the GMAT.

Learn More About Magoosh

Share Post

Email

Facebook