Carcass wrote:
The table below provides values of quadratic function f for some values x. Which of the following equations could define f(x)?
Attachment:
GRe The table below.jpg
(A)
f(x)=x2+x−1(B)
f(x)=x2−1 (C)
f(x)=−x2+x+1(D)
f(x)=−x2+1 (E)
f(x)=x2−x+1Let's eliminate answers choices by plugging easy-to-work-with numbers into each function.
For example, the table tells us that f(0) = 1, so let's plug x = 0 into each function and eliminate those that don't evaluate to 1.
We get:
(A)
f(0)=02+0−1=−1. Eliminate
(B)
f(0)=02−1=−1. Eliminate
(C)
f(0)=−(02)+0+1=1. Keep
(D)
f(0)=−(02)+1=1. Keep
(E)
f(0)=02−0+1=1. Keep
The table also tells us that, when f(1) = 0, so let's plug x = 1 into each remaining function and eliminate those that don't evaluate to 0.
We get:
(C)
f(1)=−(12)+1+1=1. Eliminate
(D)
f(1)=−(12)+1=0. Keep
(E)
f(1)=12−1+1=1. Eliminate
By the process of elimination, the correct answer is D