What is x plus y equals -8 y equals x-9?

Answer 1

-17

Answer 2

x = 0.5 and y = -8.5

This is an example of simultaneous equations. You have two equations:

1. x + y = -8

2. y = x - 9 which for the sake of simplicity we can rewrite as y - x = -9.

In order to calculate the values of x and y we first need to eliminate either the x's or the y's.

So let us get rid of the x's. As you can see in 1. we have an "x" and in 2. we have a

"-x". Therefore if we add 1. and 2. together the x and -x will cancel each other out (as x + -x = 0) and we will be left with only one variable (y).

1.x + y = -8

2. y - x = -9

Adding 1. & 2. gives us:

3. 2y = -17.

Therefore y = -17/2

y = -8.5

Now we substitute the value of y back into either 1. or 2. in order to calculate the value of x. So substituting y = -8.5 back in to 1. we get

x + -8.5 = -8

x = -8 + 8.5

x = 0.5

Thus x = 0.5 and y = -8.5