solving with elimination- nonstandard notation

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7x+8y=4

3x+2y=6

Aug 7th, 2015

Hello!

The simplest variable to eliminate is y: 8y and 2y differ by factor of 4.
Multiply the second equation by -4 and add to the first:

(7x+8y) + (-4)*(3x+2y) = 4 + (-4)*6,
7x + 8y - 12x - 8y = 4 - 24,
-5x = -20,
x = 4.

Now substitute x=4 to the, say, second equation and obtain

3*4 + 2y = 6,
2y = 6 - 12 = -6,
y = -3.

The answer is: x=4, y=-3.

Please ask if anything is unclear.
Aug 7th, 2015

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