SOLUTION: solve using the elimination method calculator -4y + 8y = 56; 2x - 3y = -21

Algebra ->  Systems-of-equations -> SOLUTION: solve using the elimination method calculator -4y + 8y = 56; 2x - 3y = -21      Log On


   



Question 416978: solve using the elimination method calculator -4y + 8y = 56; 2x - 3y = -21
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!


-4y+%2B+8y+=+56 .........I guess you have -4x here
-4x+%2B+8y+=+56
2x+-3y+=+-21

Solved by pluggable solver: Linear Systems by Addition
We'll solve the system:
-4%2Ax+%2B+8%2Ay+=+56
2%2Ax+%2B+-3%2Ay+=+-21
by elimination by addition.To eliminate by addition, we need to set both coefficients of x to numbers with changed signs, i.e a and -a. Since in the second equation we have 2 as our coefficient for x, to get 4 we have to multiply all terms of the second equation by 4%2F2 which is equal to 2.

Multiplying, we get on our second equation:%282%2A2%29x+%2B+%28-3%2A2%29y+=+-21%2A2
4%2Ax+%2B+-6%2Ay+=+-42

Adding both equations we get:

%28-4%2B4%29x+%2B+%288%2B-6%29y+=+%2856%2B-42%29

Since -4 and 4 cancel out, we have a linear equation:Therefore, we know that y = 7.

Plugging that in into the first equation gives us:

-4%2Ax+%2B+8%2Ay+=+56
-4%2Ax+%2B+8%2A7+=+56
-4%2Ax+%2B+56+=+56
-4%2Ax+=+56+-+56
x+=+%2856+-+56%29%2F-4
x+=+0%2F-4
x+=+0

Therefore, our answer is:

system%28+x=0%2C+y=7+%29