Question

x^2-4x-21=
Solve by quadratic formula

Answer 1

x² - 4x -21 = 0 = ax² + bx+c

We know that

x = [-b ± √ (b² -4ac ) ]/2a

=> x = [ 4± √ (16-4× 1 × (-21) )]/2

=> x = [ 4± √ 100 ]/2

=> x = (4±10)/2

=> x = 7 or x = -3