Question

-7x-8y=9 and -4x+9y=-22 solve by elimination method

Answer 1

Answer:

x = 1

y = -2

Step-by-step explanation:

Given:

1st equation:  -7x-8y=9  

2nd equation: -4x+9y=-22

we multiply the first equation by 4 and we multiply the second equation by -7, so that we can eliminate x and solve for y.  

1st equation:  4(-7x-8y=9 )    ------------>   -28x - 32y = 36

2nd equation: -7( -4x+9y=-22) ---------->   28x -63y = 154

then we add these two equations together, and solve for y.

 -28x - 32y = 36

  28x -63y = 154

--------------------------

 -95y =  190

 y =    190 /−95

   y = -2

substitute y = -2 to the first equation

-7x-8y=9

-7x - 8(-2) = 9

-7x + 16 = 9

-7x = 9 - 16

-7x = -7

x =  −7 /−7

​x = 1

Check:

substitute x = 1 and y = -2 to first equation

-7x-8y=9

-7(1) - 8(-2) = 9

-7 + 16 = 9

9 = 9

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