SOLUTION: solve by substitution method 9x+4y= -55 -7x+y= 51

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Question 212812: solve by substitution method
9x+4y= -55
-7x+y= 51
Found 2 solutions by drj, MathTherapy:
Answer by drj(1380) About Me  (Show Source):
You can put this solution on YOUR website!
Solve by substitution method

9x%2B4y=+-55
-7x%2By=+51
Use the following steps to solve the above system of equations:

Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++9%5Cx+%2B+4%5Cy+=+-55%2C%0D%0A++++-7%5Cx+%2B+1%5Cy+=+51+%29%0D%0A++We'll use substitution. After moving 4*y to the right, we get:
9%2Ax+=+-55+-+4%2Ay, or x+=+-55%2F9+-+4%2Ay%2F9. Substitute that
into another equation:
-7%2A%28-55%2F9+-+4%2Ay%2F9%29+%2B+1%5Cy+=+51 and simplify: So, we know that y=2. Since x+=+-55%2F9+-+4%2Ay%2F9, x=-7.

Answer: system%28+x=-7%2C+y=2+%29.



I hope the above steps were helpful.

For Step-By-Step free videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.

Good luck in your studies!

Respectfully,
Dr J

Answer by MathTherapy(10552) About Me  (Show Source):
You can put this solution on YOUR website!
9x + 4y = -55 ------ eq (i)
-7x + y = 51 ------ eq (ii)

Solve eq (ii) for y ------> -7x + y = 51 becomes y = 7x + 51

Substitute 7x + 51 for y in eq (i) 9x + 4y = -55 becomes

9x + 4(7x + 51) = -55

9x + 28x + 204 = -55

37x = -259

x+=+%28-259%29%2F37+=+-+7

Substitute - 7 for x in eq (ii) -7x + y = 51 becomes

-7(-7) + y = 51

49 + y = 51

y = 2

Therefore, the solution set is (highlight_green%28-7%29,highlight_green%282%29)