SOLUTION: how do you use a table of values to graph y=x^2-2x-8

Question 131611: how do you use a table of values to graph
y=x^2-2x-8
Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!
In order to graph , we need to plot some points. To do that, we need to plug in some x values to get some y values

So let's find the first point:

Start with the given function

Plug in

Raise -3 to the 2nd power to get 9

Multiply 1 and 9 to get 9

Multiply 2 and -3 to get -6

Subtract -6 from 9 to get 15

Subtract 8 from 15 to get 7

So when , we have

So our 1st point is (-3,7)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise -2 to the 2nd power to get 4

Multiply 1 and 4 to get 4

Multiply 2 and -2 to get -4

Subtract -4 from 4 to get 8

Subtract 8 from 8 to get 0

So when , we have

So our 2nd point is (-2,0)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise -1 to the 2nd power to get 1

Multiply 1 and 1 to get 1

Multiply 2 and -1 to get -2

Subtract -2 from 1 to get 3

Subtract 8 from 3 to get -5

So when , we have

So our 3rd point is (-1,-5)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 0 to the 2nd power to get 0

Multiply 1 and 0 to get 0

Multiply 2 and 0 to get 0

Subtract 0 from 0 to get 0

Subtract 8 from 0 to get -8

So when , we have

So our 4th point is (0,-8)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 1 to the 2nd power to get 1

Multiply 1 and 1 to get 1

Multiply 2 and 1 to get 2

Subtract 2 from 1 to get -1

Subtract 8 from -1 to get -9

So when , we have

So our 5th point is (1,-9)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 2 to the 2nd power to get 4

Multiply 1 and 4 to get 4

Multiply 2 and 2 to get 4

Subtract 4 from 4 to get 0

Subtract 8 from 0 to get -8

So when , we have

So our 6th point is (2,-8)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 3 to the 2nd power to get 9

Multiply 1 and 9 to get 9

Multiply 2 and 3 to get 6

Subtract 6 from 9 to get 3

Subtract 8 from 3 to get -5

So when , we have

So our 7th point is (3,-5)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 4 to the 2nd power to get 16

Multiply 1 and 16 to get 16

Multiply 2 and 4 to get 8

Subtract 8 from 16 to get 8

Subtract 8 from 8 to get 0

So when , we have

So our 8th point is (4,0)

-------------- Let's find another point --------------

Start with the given function

Plug in

Raise 5 to the 2nd power to get 25

Multiply 1 and 25 to get 25

Multiply 2 and 5 to get 10

Subtract 10 from 25 to get 15

Subtract 8 from 15 to get 7

So when , we have

So our 9th point is (5,7)

Now lets make a table of the values we have calculated

Now plot the points

Now connect the points to graph (note: the more points you plot, the easier it is to draw the graph)

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