x^2-4x-12 using formular method, x= (-b)+_ squareroot of b^2-4ac /2a in this equation,a=1, b=-4 , c=-12 x=-(-4)+_squareroot(-4)^2 -4×1×(-12) /2×1 x=4+_ squareroot 16+48 /2 x=4+_squareroot64 /2 x=4+_8 /2 x=4+8 /2 or x=4-8 /2 x=12/2 or x=-4/2 :.x is either 6 or -2