Question

x2 + 5x – 9 = 5Which of the following values of x satisfies the equationabove?A. 7 B. 3 C. –2 D. –7

Answer 1

The easiest way to answer this is to plug in all of the given choices to see which of them will satisfy the given equation.

$\text{ x}^2\text{ + 5x - 9 = 5}$

We get,

Choice A: 7

$\text{ x}^2\text{ + 5x - 9 = 5}$$\text{ (7)}^2\text{ + 5(7) - 9 = 5}$$\text{ 49 + 35 - 9 = 5}$$\text{ 84 - 9 = 5}$$\text{ 75 }\ne\text{ 5}$

Therefore, x is not equal to 7.

Choice B: 3

$\text{ (3)}^2\text{ + 5(3) - 9 = 5}$$\text{ 9 + 15 - 9 = 5}$$\text{15 }\ne\text{ 5}$

Therefore, x is not equal to 3.

Choice C: -2

$(-2)^2\text{ + 5(-2) - 9 = 5}$$\text{ 4 - 10 - 9 = 5}$$\text{ -15 }\ne\text{ 5}$

Therefore, x is not equal to -2.

Choice D: -7

$(-7)^2\text{ + 5(-7) - 9 = 5}$$\text{ 49 - 35 - 9 = 5}$$\text{ 5 = 5}$

Therefore, x = -7

The answer is letter D : -7