Write y= -4x^2+8x-1 in vertex form.

Question

y= (-4x^2+8x+2+16)-1+2+16
y= (-2x+4)^2+17 (answer)

Answer 1

no, the coefficient of the x term inside the bracket should be 1

so
y= -4x^2+8x-1
= -4[x^2 - 2x ] - 1
= -4[x^2 - 2x + 1 - 1] - 1
= -4[(x-1)^2 - 1] - 1
= -4(x-1)^2 + 4 - 1
= -4(x-1)^2 + 3

so the vertex is (1,3)