Solve x2 + 10x = - 21.

x = 7 and x = 3

x = - 7 and x = - 3

x = - 7 and x = 3

x = 7 and x = - 3

Answer is x = - 7 and x = - 3

x2 + 10x = - 21

x2 + 10x + 21 = 0

(x + 3) (x + 7) = 0

(x + 3) = 0

and

(x + 7) = 0

so x = - 3 and x = - 7

This is simple u just plug in the number and see if both sides r equal

7*2+10*3=-21 and this one doesn't work cuz 7*2+10*3=44

-7*2+10*-3=-21 this one doesn't work for the fact of - 7*2+10*-3=-44

-7*2+10*3=-21 this one doesn't work cuz - 7*2+10*3=16

7*2+10*-3=-21 doesn't work cuz 7*2+10*-3=-16

and so u now know nun of these answers work for ur equation