Question

For the following system, use the second equation to make a substitution for x in the first equation.

3x + 2y = 7
x - y + 3 = 0

What is the resulting equation?

3x - y - 3 + 2y = 7
3(y - 3) + 2y = 7
3y - 3 + 2y = 7

Answer 1

Ok so simply make the second equation in terms of x, so we know what x equals.

Answer 2

This means we will have to move both negative y and positive 3 to the opposite side of the equation, as we want to keep x positive.

Answer 3

As we transfer both negative y and positive 3 to the other side, the signs change to their opposite. So...

-y goes to t
and
+3 goes to -3.

Answer 4

Now we have the equation x=y-3

Answer 5

NOW we can substitute for x in the top equation.
Sub in y-3 for x in the equation 3x+2y=7

Answer 6

Now we have 3(y-3) + 2y = 7

Answer 7

Use the distributive property for 3(y-3).

This gives us 3y-9.

Now add this to the rest of the equation.

3y-9+2y = 7

Answer 8

Oh I'm sorry, we don't have to go further than 3(y-3)+2y = 7

Answer 9

DId this help?

Answer 10

yes thanks!

Answer 11

No problem