Question

Solve x2+10x+21=0 ...?

Answer 1

X²+10x+21=0
/\ = 10²-4*1*21
/\ = 100 - 84
/\ = 16
x = (-10+/-\/16)/2
x = (-10+/-4)/2
x' = (-10+4)/2 = -6/2 = -3
x" = (-10-4)/2 = -14/2 = -7
S: {-3; -7}