SOLUTION: I'm struggling to help my 8th grade daughter with her algebra........ this is one.......the solution to which system of equations has a positive y value? 4 choices are listed but

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Question 393058: I'm struggling to help my 8th grade daughter with her algebra........
this is one.......the solution to which system of equations has a positive y value? 4 choices are listed but this is the one that's supposed to be correct---
y=3x+3 and 2x+3y=0. I keep coming up with a negative value. Can you help? Thank you!
Found 2 solutions by jim_thompson5910, mananth:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
2x%2B3y=0 Start with the second equation.


2x%2B3%283x%2B3%29=0 Plug in y=3x%2B3 into the first equation. In other words, replace each y with 3x%2B3. Notice we've eliminated the y variables. So we now have a simple equation with one unknown.


2x%2B9x%2B9=0 Distribute


11x%2B9=0 Combine like terms on the left side


11x=0-9Subtract 9 from both sides


11x=-9 Combine like terms on the right side


x=%28-9%29%2F%2811%29 Divide both sides by 11 to isolate x



x=-9%2F11 Reduce




Now that we know that x=-9%2F11, we can plug this into y=3x%2B3 to find y


y=3x%2B3 Start with the first equation.


y=3%28-9%2F11%29%2B3 Substitute -9%2F11 for each x


y=-27%2F11%2B3 Multiply


y=6%2F11 Add


So the solutions are x=-9%2F11 and y=6%2F11


If you need more help, email me at jim_thompson5910@hotmail.com

Also, feel free to check out my tutoring website

Jim

Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
the solution to which system of equations has a positive y value? 4 choices are listed but this is the one that's supposed to be correct---
y=3x+3 and 2x+3y=0. I keep coming up with a negative value. Can you help? Thank you!
...
y=3x+3
y-3x=3..........................1
2x+3y=0. .......................2
...
multiply (1) by -3
we get -3y+9x=-9
add this to (2)
3y-3y+2x+9x=-9
11x=-9
/11
x= -9/11
..
plug value of x in (1)
y-3*(-9/11)=3
y+(27/11)=3
y = 3-(27/11)
y=(33-27)/11
y=6/11 which is positive
...
m.ananth@hotmail.ca