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Last Updated on May 3, 2023
GMAT OFFICIAL GUIDE PS
Solution:
The phrase “4 is one solution of the equation” means that one value of x is 4. Thus, we first must plug 4 for x into the given equation to determine the value of k. So we have
4^2 + (3)(4) + k = 10
16 + 12 + k = 10
28 + k = 10
k = -18
Next we plug -18 into the given equation for k and then solve for x.
x^2 + 3x – 18 = 10
x^2 + 3x – 28 = 0
(x+7)(x-4) = 0
x = -7 or x = 4
Thus, -7 is the other solution.
Answer: A
