Is this right or wrong check carefully and please tell me where is wrong

Is this right or wrong check carefully and please tell me where is wrong Cu __aa q b?- V b? 4 Cab

Please find below the solution to the asked query:

From given solutions ( ii )  and ( iii )  is correct Keep up the good work .

But for ( Ex. 7 ) solution is incorrect , So correct solution is , As :

First we add from given information : ( a² + 4 b² - 6 a b ) + ( a² - b² + 2 a b ) + ( b² + 6 )  + ( a² - 4 a b )

$\Rightarrow$ a² + 4 b² - 6 a b +  a² - b² + 2 a b  + b² + 6 + a² - 4 a b

$\Rightarrow$ ( a² + a² + a² ) + ( 4 b² -  b²  +  b² ) + ( - 6 a b + 2 a b - 4 a b ) + 6

$\Rightarrow$3 a² + 4 b²  - 8 a b + 6

Then we subtract " - 2 a² + b²  - a b + a " from above term , As :

$\Rightarrow$ ( 3 a² + 4 b²  - 8 a b + 6) - ( - 2 a² + b²  - a b + a )

$\Rightarrow$3 a² + 4 b²  - 8 a b + 6 + 2 a² - b²  + a b - a

$\Rightarrow$ 5 a² + 3 b²  - 7 a b - a + 6                                                      ( Ans )


Hope this information will clear your doubts about topic.