which function has a minimum value of -4?

Question

A. f(x)=2(x+2)(x-1) B.f(x)=(x-1)2 -2 C.f(x)= (x-1)(x+3) D. f(x)=-(x+3)2 E. f(x)=-2x2-8x+3 F. f(x)=1/2x2-2

Answer 1

A. f(x)=2(x+2)(x-1)

B.f(x)=(x-1)² -2

C.f(x)= (x-1)(x+3)

D. f(x)=-(x+3)²

E. f(x)=-2x²-8x+3

F. f(x)=1/2x²-2

 

All of these are parabolas. Parabolas in D & E are downward opening so they don't have any minimum.

 

So here's what YOU will do to choose the correct answer: find the x coordinate of the vertex for each parabola A, B, C or F.  I suggest that you multiply them all out so that they're all in the standard form y = ax² + bx + c.

 

Use the formula x = -b/(2a) to obtain each parabola's vertex, then evaluate f(x) with that x value. One of these results must be the =4 stated result.