Find Vx using node voltage method

[Samira]

is= 1.2 mA

i submitted my solution but it was wrong,can someone please explain why?

/* i just wanted to check if my solution is correct so i don't lose marks on my homework
did i do any mistakes ?
if so please explain.*/
my solution:

 

[CWatters]

I haven't gone through all your working but check the polarity of the 30V source and the first term in the KCL equation.

 

[gneill]

Hi Samira,

Welcome to Physics Forums!

In future be sure to use the homework formatting template that is provided in the edit window when a new thread is started here in a homework forum. It is one of the rules of the forums and you will find your posts deleted if it is not used.

Regarding your question, your work and result look fine.

 

[Samira]

alright, I'm sorry and thank you for your answer.

 

[CWatters]

I still think the first term should be (Vx - (-30)) / 5

For example to be consistent with the third term (Vx-(+80))/1

 

[gneill]

I still think the first term should be (Vx - (-30)) / 5

For example to be consistent with the third term (Vx-(+80))/1

Argh! You're right! I missed the reversed polarity on the 30 V supply Good catch.

@Samira : The first term in your node equation needs to be fixed. It should be ##\frac{V_x + 30}{5}## .

 

[Samira]

I still think the first term should be (Vx - (-30)) / 5

For example to be consistent with the third term (Vx-(+80))/1

i'm sorry i did not see your answer last night , i thought i only got one.
thank you !