+0

0
176
3

Guest Nov 25, 2014

#1
+80933
+10

"c" is easy.... it's = 7

The vertex is at (h, k) = (-1, 8)   and the point    (2. -1) is on the graph

So we have

y = a(x - h)^2 + k

-1 =a(2- (-1))^2 + 8

-1 = a(3)^2 + 8      subtract 8 from both sides

-9 = a(9)     divide both sides by 9

-1 = a

And the x coordinate of the vertex is given by  -b/2a

So we have

-1 = -b/2(-1)  →  -1 = -b/-2 →  b = - 2

So.....our function is

y = -1x^2 - 2x + 7

So

a + b + 2c =

-1 + (-2) + 2(7) =

11

CPhill  Nov 25, 2014
Sort:

#1
+80933
+10

"c" is easy.... it's = 7

The vertex is at (h, k) = (-1, 8)   and the point    (2. -1) is on the graph

So we have

y = a(x - h)^2 + k

-1 =a(2- (-1))^2 + 8

-1 = a(3)^2 + 8      subtract 8 from both sides

-9 = a(9)     divide both sides by 9

-1 = a

And the x coordinate of the vertex is given by  -b/2a

So we have

-1 = -b/2(-1)  →  -1 = -b/-2 →  b = - 2

So.....our function is

y = -1x^2 - 2x + 7

So

a + b + 2c =

-1 + (-2) + 2(7) =

11

CPhill  Nov 25, 2014
#2
+80933
0

Thanks for those points,  Melody....!!!!

CPhill  Nov 25, 2014
#3
+91436
+5

This is a really good one for high school students to look at.  (Maybe years 9 to 11)

Chris has given you a nice solution. Thanks Chris.

Melody  Nov 25, 2014

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