Question

If 9x-8y=4 and 2x-3y=-4, then what is the value of x?

Answer 1

step1; multiply first equation with 3
step2; multiply second equation with -8
step3; add the two equations
see what you get

Answer 2

9x - 8y = 4 ---> (2)9x - 8y = 4
2x - 3y = - 4--> (-9)2x - 3y = - 4
---------------
18x - 16y = 8 (result of multiplying by 2)
-18x + 27y = 36 (result of multiplying by -9)
----------------add
0 + 11y = 44
11y = 44 (divide both sides by 11)
y = 4

now sub 4 in for y in either of the original equations
2x - 3y = - 4
2x - 3(4) = - 4
2x - 12 = - 4 (add 12 to both sides)
2x - 12 + 12 = - 4 + 12 (combine like terms)
2x = 8 (divide by 2 to get x by itself)
2x/2 = 8/2
x = 4

now check by subbing in known values into either of the original equations
9x - 8y = 4
9(4) - 8(4) = 4
36 - 32 = 4
4 = 4 (correct)

ANSWER : x = 4, y = 4 or (4,4)

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