SOLUTION: Solve the linear system:4x+7y=-9 3x=3y+18

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Question 1132158: Solve the linear system:4x+7y=-9 3x=3y+18
Found 2 solutions by MathLover1, greenestamps:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

4x%2B7y=-9+.........eq.1
3x=3y%2B18++.........eq.2........solve for x
-----------------------------------

x=3y%2F3%2B18%2F3++.........eq.2
x=y%2B6++.............substitute in eq.1

4%28y%2B6+%29%2B7y=-9+
4y%2B24%2B7y=-9+
11y=-9-24+
11y=-33++
y=-3+
go to x+=y%2B6+........., substitute y
x+=-3%2B6+
x+=3
solution:
(3,-3)
+graph%28+600%2C+600%2C+-10%2C+10%2C+-10%2C+10%2C+x-6%2C+-4x%2F7-9%2F7%29+


Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


If both linear equations are given in the form Ax+By = C, solving the system by elimination is almost always easier than solving by substitution.

And if either given equation can be simplified, doing that will nearly always make the rest of the work easier.

4x%2B7y+=+-9
3x-3y+=+18 --> x-y+=+6

Multiply the second equation by 7 and add to the first equation, eliminating y:

4x%2B7y+=+-9
7x-7y+=+42
11x+=+33
x+=+3

Substitute x = 3 in either original equation and solve for y:
3-y+=+6
-y+=+3
y+=+-3

ANSWER: (3,-3)