In the second step you should have subtracted the 2x to move it to the other or side of the equals sign
Answer:

Step-by-step explanation:
The value in 
The value in 
The value in 
The answer is: 2a^4 - 3a^2 b - 5b^2
Answer:
answer is 10
Step-by-step explanation:
I think it might be 7 don't know what answers you may have but its a guess