What i need answered

Question

-4x + 9y = 9

x - 3y = -6

Answer 1

Hi Kaitlin!

The first thing we would do in this system of equations problem is to find a way to cancel out either the x's or the y's. I would recommend multiplying the entire second equation by 3, which will give us 3x - 9y = -18. Adding the two equations will cancel out the terms with y, leaving us with -x = -9. We divide both sides by -1 to cancel the negatives, and find that x = 9. We then plug this x value back into either equation, but I'll pick the second again because it's a little easier to work with. Plugging in 9 for x gives us: (9) - 3y = -6. We subtract 9 from both sides to find -3y = -15, then divide both sides by -3 to find y = 5.

We can double check our answer by plugging in 9 for x and 5 for y, and -4(9) + 9(5) = 9 checks out, as does (9) - 3(5) = -6.

In short, x = 9 and y = 5 :)

Answer 2

You can solve this set either by elimination or substitution...and it is a toss up which is easier.

If prefer elimination:

Multiply the 2nd equation by 4 and add the 2 equations.

This will give you an equation in y alone which is easy to solve.

Then go back and use the y value in either original equation to get x.