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User avatar #1 - ffx (01/22/2013) [-]
(9, -2) c:
#2 to #1 - anonymous (01/22/2013) [-]
show work
i forgot how to algebra
User avatar #7 to #2 - ffx (01/22/2013) [-]
If the sum of both is equal to 0, you can multiply them by having opposites with one of them being negative.
User avatar #6 to #2 - ffx (01/22/2013) [-]
And FJ doesn't take multiple spaces....-_- fml
User avatar #5 to #2 - ffx (01/22/2013) [-]
Look at the first equation : 2x + 9y = 0.

What is the first numbers you'd think that can cancel each other out to make it a perfect 0?

simple watch this: 2x + 9y = 0
*9 *-2

18 + -18 = 0

Now if you try it on the 3x + 5y = 17 to confirm:

3(9) + 5(-2) = 17
27 - 10 = 17
17 = 17
#3 to #2 - cnlsanders ONLINE (01/22/2013) [-]
User avatar #21 to #3 - happygrowman (01/22/2013) [-]
was that necessary?
#10 to #3 - anonymous (01/22/2013) [-]
guessing and checking works in this case because it is easy the real solutions is:
2x + 9y = 0 => 2x = -9y => x = -(9/2)y => x = -(4.5y)
now sub into other equation:
3(-4.5y) + 5y = 17 => (-13.5)y + 5y = 17 => -8.5y = 17 => y = -(1/2)
now sub y value into original equation:
2x + 9(-0.5) = 0 => 2x - 4.5 = 0 => 2x = 4.5 => x = 2.25
y = -0.5; x = 2.25
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