SOLUTION: Solve by the substitution mehtod 3x+5y=-11 -6x+y=44

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Question 145832: Solve by the substitution mehtod

3x+5y=-11
-6x+y=44
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!


Start with the given system of equations:

system%283x%2B5y=-11%2C-6x%2By=44%29



Now in order to solve this system by using substitution, we need to solve (or isolate) one variable. I'm going to solve for y.




So let's isolate y in the first equation

3x%2B5y=-11 Start with the first equation


5y=-11-3x Subtract 3x from both sides


5y=-3x-11 Rearrange the equation


y=%28-3x-11%29%2F%285%29 Divide both sides by 5


y=%28%28-3%29%2F%285%29%29x%2B%28-11%29%2F%285%29 Break up the fraction


y=%28-3%2F5%29x-11%2F5 Reduce



---------------------

Since y=%28-3%2F5%29x-11%2F5, we can now replace each y in the second equation with %28-3%2F5%29x-11%2F5 to solve for x



-6x%2Bhighlight%28%28%28-3%2F5%29x-11%2F5%29%29=44 Plug in y=%28-3%2F5%29x-11%2F5 into the first equation. In other words, replace each y with %28-3%2F5%29x-11%2F5. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.



%285%29%28-6x-%283%2F5%29x-11%2F5%29=%285%29%2844%29 Multiply both sides by the LCM of 5. This will eliminate the fractions (note: if you need help with finding the LCM, check out this solver)



-30x-3x-11=220 Distribute and multiply the LCM to each side



-33x-11=220 Combine like terms on the left side


-33x=220%2B11Add 11 to both sides


-33x=231 Combine like terms on the right side


x=%28231%29%2F%28-33%29 Divide both sides by -33 to isolate x



x=-7 Divide





-----------------First Answer------------------------------


So the first part of our answer is: x=-7









Since we know that x=-7 we can plug it into the equation y=%28-3%2F5%29x-11%2F5 (remember we previously solved for y in the first equation).



y=%28-3%2F5%29x-11%2F5 Start with the equation where y was previously isolated.


y=%28-3%2F5%29%28-7%29-11%2F5 Plug in x=-7


y=21%2F5-11%2F5 Multiply


y=2 Combine like terms and reduce. (note: if you need help with fractions, check out this solver)



-----------------Second Answer------------------------------


So the second part of our answer is: y=2









-----------------Summary------------------------------

So our answers are:

x=-7 and y=2

which form the point








Now let's graph the two equations (if you need help with graphing, check out this solver)


From the graph, we can see that the two equations intersect at . This visually verifies our answer.




graph of 3x%2B5y=-11 (red) and -6x%2By=44 (green) and the intersection of the lines (blue circle).