Question

Solve the equation x^2-4x-12=0 two ways. By factoring and by Quadratic formula

Answer 1

By factoring, find two values j and k which satisfy two conditions, jk=ac=-12 and j+k=b=-4, so j and k must be 2 and -6 so the factors are:

(x+2)(x-6)=0

So x=-2 and 6

By the quadratic formula, x=(-b±√(b^2-4ac))/(2a), in this case:

x=(4±√(16+48))/2

x=(4±√64)/2

x=(4±8)/2

x=2±4

x=-2 and 6