-7x-8y=9 -4x+9y=-22?

or:-7x-8y=9 -4x+9y=-22?or:X=1.6Y=-1.35or:These are called simultaneous equations. What you need to do is manipulate them somehow so that you can get

or:-7x-8y=9 -4x+9y=-22?

or:X=1.6Y=-1.35

or:These are called simultaneous equations. What you need to do is manipulate them somehow so that you can get an equation that only deals in one variable (x or y) rather than both (x and y in the same equation). Let's write out what we've got so far:-7x - 8y = 9-4x + 9y = -22Multiply the first equation by -4 (it'll still be true):28x + 32y = -36For the second equation (-4x + 9y = -22), multiply this by 7.-28x + 63y = -154The two equations together are now:28x + 32y = -36-28x + 63y = -154Notice you've got 28x in both equations (once negative, once positive). We've made this happen on purpose by multiplying one by -4 and one by 7. If we add the two equations together, the 28x and -28x will cancel each other out. So:(28x - 28x) + (32y + 63y) = -36 -154Or:95y = -190y = -2Now we know y, we can go back to either of the original equations and substitute it:-7x - 8y = 9-7x - (8 x -2) = 9-7x - (-16) = 9-7x + 16 = 9-7x = -77x = 7x = 1If we test both equations with x=1, y=-2, you'll find they both work.

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