Solution - Simplification or other simple results

Step  1  :

Step  2  :

Pulling out like terms :

 2.1    Simplify ( -7x-4y )²

Put the exponent aside and simplfy the base by pulling out like factors :
 -7x-4y  =  -1 • (7x+4y) 

Remember the 4th law of exponents : (a • b)^m= a^m• b^m

Retract the exponent and apply the 4th law to the simplified base: ( -1 • (7x+4y) )² =  (-1)² • (7x+4y)²  

Final result :

  (7x + 4y)2