From m2 + 5m - 7 subtract m2 - 3m 4. a) 8m - 3 b) 2m - 11 c) 2m2 + 2m - 11 d) 2m2 + 8m - 11

The answer is:  [A]:  " 8m − 3 " .

Explanation:


(m² + 5m − 7) − (m² − 3m − 4) =

    (m² + 5m − 7) − 1(m² − 3m − 4)  =

     (m² + 5m − 7) − 1m²  + 3m + 4) =

m² + 5m − 7 − m²  + 3m + 4 ;


Now, combine the "like terms" :

m² − m² = 0 (cancel out).

+5m +3m = +8m ;

− 7 + 4 = -3 ;

And we are left with:

 " 8m − 3 " ;  which is: Answer choice:  [A] .