Solve Substitution Problem: x^2+2y^2=9, x-y+3=0 with x=(-1,-3) and y=(2,0)

[wat2000]

x^2+2y^2=9
x-y+3=0

I have x=(-1,-3) y=(2,0)

I don't want to have to write out the whole problem I just want to know if this is correct

Can someone tell me if this is correct?

 

[symbolipoint]

Does the graph make sense based on your two solution points?

Does EACH solution point for (x, y) satisfy BOTH equations?

 

[wat2000]

Ive tried to graph but it won't show up on my graph. shouldn't it be y=(sqrt-1/2x^2-9/2) y=(-sqrt-1/2^x2-9/2) y=x+3

 

[wat2000]

Wait its +9 not-9. Yes when I plug it into my calculator I find the points x=(-1,-3) y=(2,0)

 

[Mark44]

You don't have to graph anything. All you need to do is verify that x = -3, y = 0 is a solution of both equations, and that x = -1, y = 2 is a solution of both equations.

That is equivalent to (-3, 0) and (-1, 2) being the intersecting points of both graphs.

You should not write solutions this way:

I have x=(-1,-3) y=(2,0)

When people see ordered pairs, as above, they usually assume that the first number is the x coordinate and the second is the y coordinate.

 

[HallsofIvy]

x^2+2y^2=9
x-y+3=0

I have x=(-1,-3) y=(2,0)

This is not a very good way of writing the answer. First, it is easy to think, as Mark44 says, that the pair is (x, y).

Further, a "solution" is not just a value of x and a value of y, it is a specific x and y pair. That is, x= -1 and y= n2 is a solution but x= -1 and y= 0 is not. x= -2 and y= 0 is a solution but x= -1 and y= 0 is not. Better to write the solutions as (x, y)= (-1, 2) and (x, y)= (-3, 0).

I don't want to have to write out the whole problem I just want to know if this is correct

Can someone tell me if this is correct?