The solutions to the quadratic equation are : C. x = 3 and D. x = -7
What is a quadratic equation?
A quadratic equation is the second-order degree algebraic expression in a variable. the standard form of this expression is ax² + bx + c = 0 where a. b are coefficients and x is the variable and c is a constant.
We have to apply the quadratic formula:
For: ax² + bx + c = 0
x =[ -b ± √b²-4ac] /2a
Given; x^2 + 4x - 21 = 0
Replacing with the values given:
x =[ -4 ± √(4)²-4(1)-21] /2(1)
x = [-4 ± √16 +84] /2
x = [ -4 ± √100] /2
x = [ -4 ± 10] /2
Positive:
x = [-4 + 10] /2 = 6 /2 = 3
Negative:
x = [ -4 - 10] /2 = -14/2 = -7
So, the solutions are :
C. x = 3 and D. x = -7
Learn more about quadratic equations;
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