Answer:
vertex (-4,-18)
Step-by-step explanation:
f(x)=2(x+1)(x+7)
f(x)=2(x^2+8x+7)
f(x)=2x^2+16x+14
f(x)=2(x^2+8x)+14
f(x)=2(x^2+8x+4^2-4^2)+14
f(x)=2(x^2+8x+4^2)+2(-4^2)+14
f(x)=2(x^2+8x+4^2)+2(-4^2)+14
f(x)=2(x^2+8x+4^2)-18
f(x)=2(x+4)^2-18
vertex form:
f(x)=a(x-h)^2+k
h=-4
k=-18
vertex (-4,-18)
