SOLUTION: solve the system by substitution for the following problem: x+8y=-7 8x+9y=7 also need to see what ths looks like on a graph? Thank you

Algebra ->  Coordinate Systems and Linear Equations  -> Lessons -> SOLUTION: solve the system by substitution for the following problem: x+8y=-7 8x+9y=7 also need to see what ths looks like on a graph? Thank you      Log On


   

Question 212996: solve the system by substitution for the following problem:
x+8y=-7
8x+9y=7
also need to see what ths looks like on a graph?
Thank you
Found 2 solutions by drj, Earlsdon:
Answer by drj(1380) About Me  (Show Source):
You can put this solution on YOUR website!
Solve the system by substitution for the following problem:
x+8y=-7
8x+9y=7
Also need to see what this looks like on a graph?

Here are the following steps to solve the system of equations by substitution.

Solved by pluggable solver: SOLVE linear system by SUBSTITUTION
Solve:
+system%28+%0D%0A++++1%5Cx+%2B+8%5Cy+=+-7%2C%0D%0A++++8%5Cx+%2B+9%5Cy+=+7+%29%0D%0A++We'll use substitution. After moving 8*y to the right, we get:
1%2Ax+=+-7+-+8%2Ay, or x+=+-7%2F1+-+8%2Ay%2F1. Substitute that
into another equation:
8%2A%28-7%2F1+-+8%2Ay%2F1%29+%2B+9%5Cy+=+7 and simplify: So, we know that y=-1.14545454545455. Since x+=+-7%2F1+-+8%2Ay%2F1, x=2.1636363636364.

Answer: system%28+x=2.1636363636364%2C+y=-1.14545454545455+%29.



Here is the graph. Note the solution (x,y) as the intersection between the two lines.

graph%28+300%2C+200%2C+-5%2C+5%2C+-5%2C+5%2C+%28-x-7%29%2F8%2C+%28-8x%2B7%29%2F9+%29

I hope the above steps were helpful.

For FREE Step-By-Step 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 Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Solve:
x%2B8y+=+-7 Rewrite this as: x+=+-8y-7 and substitute into the second equation.
8x%2B9y+=+7
8%28-8y-7%29%2B9y+=+7 Simplify the left side.
-64y-56%2B9y+=+7
-55y-56+=+7 Add 56 to both sides.
-55y+=+63 Divide both sides by -55.
y+=+-63%2F55 Now substitute this into the first equation and solve for x.
x%2B8%28-63%2F55%29+=+-7
x-%28504%2F55%29+=+-7
x+=+119%2F55
x+=+2.164
y+=+-1.145
graph%28400%2C400%2C-5%2C5%2C-5%2C5%2C-%281%2F8%29x-7%2F8%2C-%288%2F9%29x%2B7%2F9%29