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# Help with equation Watch

1. How can i solve this?
x^2 + y^2 = 9
x+ y = 2
2. When you have two simultaneous equations and one is linear / simpler than the other (does not contain any squared terms) you can solve them by substitution.

Rearrange the simpler one to make x or y the subject, for example y = 2 - x (by subtracting x from both sides)

Can you see how that will help with the substitution method?
3. (Original post by warmmuffin)
How can i solve this?
x^2 + y^2 = 9
x+ y = 2
Rearrange the bottom to get y = 2 - x, then substitute this into the top one.
Solve the resulting equation for x and then find the values of y.
4. (Original post by warmmuffin)
How can i solve this?
x^2 + y^2 = 9
x+ y = 2
One is a simultaneous equation, the other is a linear equation.
What do you do, you rearrange the linear equation to get one of the values and substitute them into the simultaneous equation.

x^2 + y^2 = 9
x+ y = 2

If I, change this into y = 2 - x.
Therefore, substitute it into the linear equation and carry on, remember (2-x)^2 is not 4 - x^2, remember how to square something in brackets, looks like the difference of squares, but it is slightly different.

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