Question

If you were to use the substitution method to solve the following system, choose the new equation after the expression equivalent to y from the first equation is substituted into the second equation.

12x - y = -4
4x - 3y = -6

4x - 3(-12x - 4) = -6
4x - 3(12x + 4) = -6
4(12x + 4) - 3y = -6
4(-12x - 4) - 3y = -6

Answer 1

@matricked

Answer 2

Do you know how to isolate y by itself on one side of the equation in the first equation?

Answer 3

4x - 3(12x + 4) = -6

Answer 4

12x - y = -4
-12x -12x
-y = -4 - 12x
divide by -1
y = 4 + 12x
@Cosmichaotic

Answer 5

Perfect! Ok give me one sec here.

Answer 6

i already got the answer but thank you

Answer 7

Ok so now that we know what "y" is equal too.
(You found 'y' to be equal to 4 + 12x or y = 4 + 12x)

We plug in 4 + 12x for y in the 2nd equation.

4x - 3y = -6 (Second Equation)

Can you show me what it would look like after you do this?

Answer 8

Tip: When you substitute like this, try to always use parentheses around what you are plugging in.

y = 4 + 12x
When you plug it in for y, make sure you plug in (4 + 12x) with parentheses. It will help you do the math correctly and more easily.

Answer 9

Go ahead and plug in
4 + 12x for y

into

4x - 3y = -6

Answer 10

Oh alright, well would you like me to continue so you can see how to do this in the future for tests, quizzes, and more importantly for your own confidence? =0)

Answer 11

If not, that's alright.