Nick wrote the function p(x) = 17 + 42x – 7x2 in vertex form. his work is below.
p(x) = –7x2 + 42x + 17
p(x) = –7(x2 – 6x) + 17
= 9;
p(x) = –7(x2 – 6x + 9) + 17
p(x) = –7(x – 3)2 + 17
when nick checked his work it did not match the standard form function. analyze nick’s work. what was his mistake?
in step 1, he did not put the function in standard form correctly.
in step 2, he should have also factored –7 from the constant term, 17.
in step 3, he did not subtract –7(9) to keep the function equivalent.
in step 4, he did not write the perfect square trinomial correctly as a binomial squared.