Linear equations

[irish]

I need a solution set for
.5x+4y=-1 and x+2.5y=3.5

Is there one?

OK this is what I did:

I first looked at the second equation and found that x=3.5-2.5y

I then substitute d 3.5-2.5y in the first equation and found that y=1

I then substituted y=1 into the second equation and found that x=1

But then when I substitute those numbers back into the equations the equations don't work.

 

[fasteddie65]

Using my graphing calculator, I find that the solution is (6, -1).
Recheck your algebra; it should work out.

 

[masters]

I need a solution set for
.5x+4y=-1 and x+2.5y=3.5

Is there one?

OK this is what I did:

I first looked at the second equation and found that x = 3.5 - 2.5y

I then substitute d 3.5 - 2.5y in the first equation and found that y = 1

I then substituted y = 1 into the second equation and found that x = 1

But then when I substitute those numbers back into the equations the equations don't work.

Hello Irish,

Looks like you just missed the negative sign on your y value. It should be y = -1.

Then when you substitute back into x = 3.5 - 2.5y, you should get the correct valule for x as well.

Good luck.

 

[Denis]

I need a solution set for
.5x+4y=-1 and x+2.5y=3.5

Make your life easier; get rid of decimals by mutliplying by 2:
x + 8y = -2 : x = -2 - 8y [1]
2x + 5y = 7 [2]

Substitute [1] in [2]