Question

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1. Solve the System of Equations:-10x-3y=-18

-7x-8y=11

[ A) (-7,-10) ]


B) (3-4)


C) (-4,-3)


D) (2,-1)


2. Solve the following system of equations by graphing: -4x+3y=12

-2x+3y=-18
[ A) (2.67,-2) ]


B) (1,-5.33)


C) (-3,-8)


D) (-15.-16)


3. What is the solution to the system of equations?

y=3x+7

y-x-9

A) (-1,-10)


B) (-17,-8)


C) (4,19)


[ D) (-8,-17) ]

Answer 1

3. D)
`(-8, -17)`

2. D)
`(-15, -16)`

1. B)
`(3, -4)`

Explanation:

3.

{y = 3x + 7

{y = x - 9

x - 9 = 3x + 7

-3x - 3x

____________

−2x - 9 = 7

+ 9 + 9

__________

−2x = 16

____ __

−2 −2

`-8 = x`[Plug this back into both equations above to get the y-coordinate of −17];
`-17 = y`

__________________________________________________________

2.

{−4x + 3y = 12

{−2x + 3y = −18

−½[−4x + 3y = 12]

{2x - 1½y = −6 >> New Equation

{−2x + 3y = −18

_______________

1½y = −24

____ ____

1½ 1½

`-16 = y`[Plug this back into both equations above to get the x-coordinate of −15];
`-15 = x`

__________________________________________________________

1.

{−10x - 3y = −18

{−7x - 8y = 11

−⅜[−7x - 8y = 11]

{−10x - 3y = −18

{2⅝x + 3y = −4⅛ >> New Equation

_________________

−7⅜x = −22⅛

______ _____

−7⅜ −7⅜

`3 = x`[Plug this back into both equations above to get the y-coordinate of −4];
`-4 = y`

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