can anyone please show me how do we get :
VOUT = [R3/(R1+R3)] [(R4 + R2)/R2] V1 - [R4/R2] V2

using superposition theorem.

 

V2=0 ==> Vout1=(R3/(R3+R1))*(R4/R2)*V1
V1=0 ==> Vout2=-(R4/R2)*V2
Vout=Vout1+Vout2

 

Okey ! so how do we get it?!!
can you see me the equivalent circuit when V2=0 ?

 

See

 

can you see me the equivalent circuit when V2=0 ?

that's simply a non-inverting amplifier.

 

I am sorry.
OUT=X*(R4/R2+1) and Vout1=(R3/(R3+R1))*(R4/R2+1)*V1=(R3/(R3+R1))*((R4+R2)/R2)*V1