Решите ! а) х^2-2х-63=0 б) 2х^2-50=0 в) х^2+9х=0 г) 7х^2-х-8=0 ^2-это квадрат

X^2 - 2x - 63 = 0
D = 4 + 252 = 256 = 16^2 
x1 = ( 2 + 16 ) : 2 = 9
x2 = ( 2 - 16 ) : 2 = - 7

2x^2 - 50 = 0
2( x^2 - 25 ) = 0
2( x - 5 )( x + 5 ) = 0
x1 = 5 
x2 = - 5 

x^2 + 9x = 0
x( x + 9 ) = 0
x1 = 0
x2 = - 9

7x^2 - x - 8 = 0
D = 1 + 224 = 225 = 15^2 
x1 = ( 1 + 15 ) : 14 = 16/14 = 8/7 = 1 1/7
x2 = ( 1 - 15 ) : 14 = - 1