Question

3x+2y=-9
-10x+5y=-5


solve using procces of elimation

Answer 1

start by multiplying equation 1 by 5 and equation 2 by 5
then subtract to eliminate y

Answer 2

so in the first equation do i multiply by 5?

Answer 3

yes - dont forget multiply every term by 5

Answer 4

Ok thank you =D

Answer 5

give it a go

Answer 6

you need to multiply equation 1 by some number (call it A) and equation 2 by some other number (call it B) such that either the coefficients of x or y become the same.

Answer 7

so for x (for example) we need 3A = 10B
or for y, we need 2A = 5B

Answer 8

can you think of what A and B should B to make either of these two equal?

Answer 9

No

Answer 10

ok, lets say we want to eliminate y, then we need to find two numbers A and B such that:
2A = 5B

we could pick A=5 and B=2 to get:
2*5 = 5*2

Answer 11

so now if we multiply the first equation by 5 and the second one by 2 we get:
5(3x + 2y) = 5(-9) ==> 15x + 10y = -45
2(-10x + 5y) = 2(-5) ==> -20x + 10y = -10

Answer 12

now we have two equations where the coefficients of y are the same, so we can subtract one from the other to eliminate y.
do you know how to do that?

Answer 13

15x + 10y = -45 - equation 3
-20x + 10y = -10 - equation 4

equation 3 minus equation 4 will give us:
(15 - (-20))x = -45 - (-10)
(15 + 20)x = -45 + 10
35x = -35
x = -1

you can now substitute this back into either your first or second equation to find y.