Question

Which ordered pair is a solution for the system of equations?

{ 3x - 5y = 15
{ 2x - y = -4

A) (-5, -6)

B) (0, 3)

C) (2, 8)

D) (-6, -11)

Answer 1

To solve this you would first multiply the second equation by -5 to get
3x - 5y = 15
-10x + 5y = 20
Then you add them both together to get
-7x=35
now divide each side by -7 to get
x=-5
Now we have our x we can look at the answers to see which one could be right. It looks like A has -5 as x so we can choose that one. If you want to find y also you can always plug in x into the first equation to figure it out. Hope this helped ^^

Answer=A

Answer 2

I don't like to eliminate this one

I will use subsitution

take 2nd equation and add 4+y to both sides
2x+4=y
sub 2x+4 for y in top equation

3x-5(2x+4)=15
3x-10x-20=15
-7x-20=15
add 20 to both sides
-7x=35
divide both sides by -7
x=-5

sub back

2x+4=y
2(-5)+4=y
-10+4=y
-6=y

x=-5
y=-6
(x,y)
(-5,-6)


A is answer