Question

What is the vertex for the graph of y = 3x2 - 12x + 9?
a.(-2, 21)
b.(-2, 45)
c.(2, -3)
d.(2, -9)

Answer 1

Do you know about the shortcut ?

Answer 2

-b/2a

Answer 3

no i didnt know

Answer 4

Use -b/2a to find the x-vertex.

Answer 5

i mean the x-cordinate of vertex.

Answer 6

i do not know how...

Answer 7

ax^2 + bx + c

If you compare, a = 3, b = 12, c = 9
\[-\frac{b}{2a} \to - \frac{12}{2(3)} \to -\frac{12}{6} \to -2\]

Answer 8

ok now what ?

Answer 9

that is the x cordinate. now insert that value in the equation to get the value of y.

Answer 10

i guess it will be easier after differentiation.. to understand, i mean

Answer 11

im so confused

Answer 12

u know about differentiation? @Andrewww ?

Answer 13

no i do not(:

Answer 14

oh, then.. saifoo's process is best for u, i guess ^^

Answer 15

bleeehhh i dont get it.

Answer 16

hey, have you come accross the quadratic equation and

\[ax^2+bx+c=0\]

Answer 17

this helps you to know what a,b and c are, thats what the rest of the people have been talking about so far

Answer 18

so in your equation \[3x^2-12x+9=0\] a=3 b=-12 c=9 are you with me so far?

Answer 19

get back to me when you are ready

Answer 20

sorry lol i was eating and im back

Answer 21

so the answer is \[\frac{-b}{2a} \rightarrow \frac{-(-12)}{2 \times 3} \rightarrow \frac{12}{6} = 2\]

Answer 22

okay

Answer 23

its just a case of knowing where to get a,b and c and put those values in the formula to give you the answer. Later you will learn exactly why it works, but for now just do the plugging in.

Answer 24

now you have the value for x can you find the value for y

Answer 25

thankkkkkkks your much more help<3

Answer 26

\[3x^2-12x+9 \rightarrow 3(2)^2-12(2)+9 = 12-24+9 =-3\] the final answer is then

(2,-3) which is answer C

Answer 27

YOUR A MATH GOD!(:

Answer 28

Nope, there are much better people here, just glad to help. :D

Answer 29

way to take a compliment<3