Convert from standard to vertex form:

Question

(x+5)(x+4)

x^2+ 9x + 20
(x+3)^2 + 20 - 9
(x+3)^2 + 11 <------

Answer 1

not quite. since (x+a)^2 = x^2+2ax+a^2,

x^2+9x = x^2+9x+(9/2)^2-(9/2)^2

x^2+9x+20
= (x + 9/2)^2 + 20-81/4
= (x + 9/2)^2 + 319/4

Answer 2

One question:

Shouldn't the answer be (x + 9/2)^2 -1/4 ?

Because 20 - (81/4) = -0.25

Answer 3

I agree with you

x^2+9x+20
= x^2 + 9x + 81/4 - 81/4 + 20
= (x+9/2) + 20 - 81/4
= (x+9/2)^ - 1/4

Answer 4

Thank you!