Question

Use the substitution method to solve this system.

y = 2x + 4
3x + y = 9

x = -1
y = 6

x = 6
y = -1

x = 6
y = 1

x = 1
y = 6

Answer 1

The result is
`x=1, y = 6`, the last option.

Explanation:

We have the following system:

`1) y = 2*x + 4`

`2) 3x + y = 9`

The substitution method is a method in which we choose one equation, write one variable in function of the other, and then replace it in the second equation to find one variable. Then, with the result, you go back to the first equation, and find the other variable.

Solution:

In 1), we already have y as a function of x. So, i am going to replace this in equation 2), so we can find x.

`y = 2*x + 4`

`3x + y = 9`

`3x + 2x + 4 = 9`

`5x = 5`

`x = (5)/(5)`

`x = 1`

Now that we have the value of x, i am going back to equation 1) to find the value of y

`y = 2*x + 4`

`x = 1`

`y = 2*1 + 4`

`y = 6`

The result is
`x=1, y = 6`, the last option.