Question

Identify the solutions to the quadratic equation

x2 + 4x-21 = 0
Check all that apply
O A. x= 3
B. X= -7
O C. x = 21
O D. x= -5
O E. x= 4

Answer 1

Explanation:

Solving quadratics is easy. With no coefficient to the x^2, we can go right to finding factors. We want two numbers that multiply to -21, and add to 4. Our numbers are 7, and -3. Now, we move the numbers around to be (x-3) and (x+7). We know that these both equal 0, so we can do basic algebra to solve for x. We can subtract 7 to the other side to just get x, and add 3 over because it is subtracted by x. This leaves us with our answers:

x = -7, x = 3