x^2+12x-13=0
= x2 + 13x - x - 13 = 0
= x ( x + 13 ) - ( x + 13 ) = 0
= ( x - 1 ) ( x + 13 )
= 0
= x = 1
= x = -13
Hok tốt
x2+12x=13
xx+12x=13
x.(12+x)=13
x=0
hoặc x+12=0=> x= -12
Vậy, x = 0 hoặc x =-12
\(x^2+12x-13=0\)
\(\Leftrightarrow x^2+13x-x-13=0\)
\(\Leftrightarrow x\left(x+13\right)-\left(x+13\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+13\right)=0\Leftrightarrow x=1;x=-13\)