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Solve the system of linear equations by substitution.

−2x−5y=3
3x+8y=−6

1 Answer

3 votes
first you want to know what y or x is i chose y for this on

so the equation i'm going to use is -2x-5y=3
i want to solve for y

-2x-5y=3
+2x +2x

-5y=2x+3
/-5 /-5 /-5
y=-2/5x+-3/5

Now that i solved for y we substitute our answer into the next equation to solve for x like this:

3x+8y=-6
3x+8(-2/5x+-3/5)=-6
3x+ -3.2x+-4.8=-6
-0.2x+-4.8=-6
+4.8 +4.8
-0.2x=-1.2
/-0.2 /-0.2
x=6

After you know what x is you substitute it in for any of the equations that we started with. I picked 3x+8y=-6 to find y.

3x+8y=-6
3*6+8y=-6
18+8y=-6
-18 -18
8y=-24
/8 /8
y=-3

Since we know what x and y are we substitute it with any of the equations that we started with. i picked -2x-5y=3

-2*6-5*-3=3
-12- -15=3
3=3
so our solution (6,-3) works

User Dnomyar
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