Carcass wrote:
If 4 is one solution of the equation \(x^2 + 3x + k = 10\), where k is a constant, what is the other solution?
(A) -7
(B) -4
(C) -3
(D) 1
(E) 6
Let's first determine the value of k.
Since x =
4 is a solution to the equation x² + 3x + k = 10, we know that x =
4 SATISFIES the equation.
That is:
4² + 3(
4) + k = 10
Evaluate to get: 16 + 12 + k = 10
Solve for k to get: k =
-18So, the ORIGINAL equation is x² + 3x + (
-18) = 10
This is the same as: x² + 3x - 18 = 10
We now need to solve this equation.
First, set it equal to zero: x² + 3x - 28 = 0
Factor: (x + 7)(x - 4) = 0
So, x = -7 or x = 4
We already know that x = 4 is one solution.
So, the other solution is x = -7
Answer: A
Cheers,
Brent