Question

Here are Janet's steps for solving the system below by eliminating x. Is she correct? If not, why not?

2x + 3y = -1

5x + 8y = 0

Step One: Multiply the first equation by 5 to get 10x + 15y = -5

Step Two: Multiply the second equation by -2 to get -10x - 16y = 0

Step Three: Add the two equations to get y = -5

Step Four: Substitute x back into the first equation to get 2x + 3(-5) = -1

Step Five: Solve for x by getting 3x + 15 = -1

so 3x = -16 and x = -16/2

Answer 1

Check your step 3.

Answer 2

ok

Answer 3

Wait, I don't understand.

Answer 4

The left hand side working would be:
10x+15y-10x-16y
and that works out to be -y

Answer 5

The RHS would be
-5+0
and that works out to be -5

Answer 6

so you have -y=-5
or y=5

Answer 7

Wait, What?