Question

Помогите решить!!!!!!!!!
х² - 10х+21=0

Answer 1

D=100-84=16
x1=(10+16)/2=13
x2=(10-16)/2=-3

Answer 2

х² - 10х+21=0
x12=(10+-корень(100-4*21))/2=(10+-4)/2=3 7
x=3
x=7
(x-3)(x-7)=0