# How do you solve by substitution # x+-y=1# and #-2x+y=4#?

##### 1 Answer

The problem has two solutions:

#### Explanation:

To solve by substitution, we isolate one of the variables in one equation, and use that to solve the other equation.

**Case 1:**

Our system is:

Since the first equation is easier to work with, we can isolate a variable there.

Now, we substitute

We now know the value of

Therefore, the solution to Case 1 is

**Case 2:**

Our system is:

Like before, we isolate one of the variables in one equation and solve using the other equation.

At this point, we know the

Therefore the solution to case 2 is

The problem has two solutions: