SOLUTION: For problems 7 and 9, solve the system of equations using ADDITION to eliminate one variable. If the system has no solution, indicate that is is inconsistent. If it has infinite

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Question 359618: For problems 7 and 9, solve the system of equations using ADDITION to eliminate one variable. If the system has no solution, indicate that is is inconsistent. If it has infinite solutions, indicate that it is dependent. If the system has a solution, CHECK YOUR ANSWER.
7. 4x-3y=17
5x+y=7
CHECK (if possible)
Please help me!! I am so stuck I don't know what to do!! Thank you! :)
Answer by mathtutor19(8) (Show Source):
You can put this solution on YOUR website!
First you have to pick a variable to eliminate. I would pick y because one the them is negative. So, then you need to get the y's to equal each other so you multiply the entire bottom equation by 3 (even the answer). Then you add the x's together and the constants together and divide by the number in front of x. To find x. Then plug the x into the original equation to find y. You find y by subtracting the x on both sides of the equal sign then by dividing by the number in front of y (if there is one).
3(5x+y=7)
15x+3y=51
+7.4x-3y=7
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22.4x =58
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22.4 22.4
(I put 58/22.4 into my calculator and turned it into a fraction)
x=95/56
5(95/56)+y=7
475/56+y=7
-y -y
83/56=7-y
-7 -7
725/56-7=y
83/56=-y
---- ----
-1 -1
-83/56=y