Question

Write the quadratic function in vertex form.

y = x^2 + 18x + 71

y = (x - 9)^2 - 10

y = (x + 9)^2 - 10

y = (x + 9)^2 + 10

y = (x - 9)^2 + 10

Answer 1

so its basically completing the square,
have heard of it?

Answer 2

I've heard of it , yes

Answer 3

ok, in this method, you add and subtract this term,
"[(1/2)*co-efficient of x]^2"
so, whats the co-efficient of 'x' here?

Answer 4

1

Answer 5

umm...no,
co-efficient of 'x' is the number multiplied with 'x' (not x^2)

Answer 6

so....

Answer 7

18?

Answer 8

yes!
1/2*18 =...?

Answer 9

and its square = ...?

Answer 10

wait what?

Answer 11

ok, step by step :P
1/2 *18 = ...?

Answer 12

9

Answer 13

yes,
2nd last step :
9^2= ... ?

Answer 14

81

Answer 15

last step:
retriceand subtract 81 to y = x^2 + 18x + 71
y = (x^2 + 18x +81) -81+71

what can you tell about (x^2 + 18x +81) ?

Answer 16

i meant "add and subtract"

Answer 17

I don't know :( i'm lost

Answer 18

did you get this?
v

Answer 19

y = (x^2 + 18x +81) -81+71

Answer 20

yes .

Answer 21

ok, so you know \(a^2+2ab+b^2=(a+b)^2\)
?

Answer 22

kinda , yeah

Answer 23

can i say
\((x^2 + 18x +81) = (x+9)^2\)

Answer 24

yes

Answer 25

so, which choice will you choose now ?

Answer 26

c?

Answer 27

\(y = (x^2 + 18x +81) -81+71=(x+9)^2-10\)
not b?

Answer 28

yeah b , sorry I got them mixed up

Answer 29

no porbelm :)