Question

The quadratic function f(x) = ax² + bx + c has tge minimum point (-2,-9) ans f(-1) = -7 Find (a) values of a,b and c

Answer 1

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"katie deleted your answer to the question Hello,a=2, b=8, c=-1Indeed,y=f(x)=ax...

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Answer is a=2, b=8 and c=-1

Indeed:

y=f(x)=ax²+bx+c

Since (-2,-9) is the vertex,

y=k*(x+2)²-9

Or f(-1)=-7 ==> -7=k*(-1+2)²-9 ==> k=2

f(x)=2(x+2)²-9=2*(x²+4x+4)-9=2x²+8x+8-9

f(x)=2x²+8x-1

A proof: the picture is following.