х² + 18х - 63 = 0
х² + 21х - 3х - 63 = 0
х * (х + 21) - 3 * (х + 21) = 0
(х + 21) * (х - 3) = 0
х + 21 = 0; х - 3 = 0
= - 21, = 3
Объяснение:
x^2+18x-63=0
D = 324 + 252 = 576
√576 = 24
x = (-18±24)/2 = 3 ; -21
= - 21, 
= 3
