Ok, first group x terms f(x)=(x²+4x)-8 factor out quadratic coefient (no need but that's the step) f(x)=1(x²+4x)-8 take 1/2 of the linear coefient and square it 4/2=2, (2)²=4 add positive and negative of it insides the parenthasees f(x)=1(x²+4x+4-4)-8 factor perfect square f(x)=1((x+2)²-4)-8 distribute f(x)=1(x+2)²-4-8 f(x)=1(x+2)²-12 and, now if we wanted to find the x intercepts where f(x)=0 then 0=1(x+2)²-12 12=(x+2)² +/-2√3=x+2 -2+/-2√3=x
x=-2+2√3 or -2-2√3 that is where the x intercept are
