Question

MEDAL HELP PLEASE http://gyazo.com/746c18162b0dcbc563c5743166573f60

Answer 1

@jim_thompson5910

Answer 2

first you need to find the x coordinate of the vertex

use the formula x = -b/(2a)

Answer 3

f(x) = -5x^2 - 20x - 10 is in the form y = ax^2 + bx + c

a = -5
b = -20
c = -10

Answer 4

so you'll plug a = -5 and b = -20 into x = -b/(2a) to get x = ??

Answer 5

x = -100?

Answer 6

no you divide, not multiply

Answer 7

/ means division

Answer 8

-2

Answer 9

now plug that into f(x) to get f(-2) = ???

Answer 10

100- (-40) - 100?

Answer 11

10*

Answer 12

so because f(-2) = 10, we know the vertex is the point (-2,10)

Answer 13

vertex: (h,k) = (-2,10) ----> h = -2 and k = 10

Answer 14

vertex form:

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

y = -5(x-(-2))^2 + 10

y = -5(x+2)^2 + 10

Answer 15

thats it?

Answer 16

what is the axis of symmetry?

Answer 17

not sure

Answer 18

x = h is the axis of symmetry in general

Answer 19

2

Answer 20

remember the form is x - h

Answer 21

go back where I state what the vertex is

Answer 22

dont get it

Answer 23

where I said (h,k)

Answer 24

-2,10

Answer 25

so h = ???

Answer 26

-2

Answer 27

h is the x coordinate of the vertex

it also helps form the axis of symmetry

Answer 28

so the axis of symmetry is x = -2

Answer 29

http://gyazo.com/42f0e990ff96d3e4edc89ca44ba1844c and help on this please

Answer 30

are you familiar with the AC method?

Answer 31

no

Answer 32

ok go ahead and read this

https://people.richland.edu/james/misc/acmeth.html

it provides the basic idea and some examples

Answer 33

not sure how to start it

Answer 34

@jim_thompson5910

Answer 35

what are a,b, & c?

Answer 36

a = -15 b = 2 c = x

Answer 37

a = 2
b = 1
c = -15

Answer 38

what is a*c equal to?

Answer 39

0

Answer 40

no

Answer 41

30

Answer 42

-30

Answer 43

closer, but no

Answer 44

yeah -30

Answer 45

now you need to find two numbers that

a) multiply to -30

AND

b) add to 1

Answer 46

15 x -2
0 + 1

Answer 47

notice how 15 plus -2 = 13

we want the two numbers to add to 1 as well

Answer 48

6 x -5

Answer 49

@jim_thompson5910

Answer 50

very good

Answer 51

so break up 1x into 6x - 5x

Answer 52

we now have 2x^2 + 6x - 5x - 15 = 0

factor by grouping

Answer 53

are you familiar with factor by grouping?

Answer 54

yes but this one is confusing