Question

Q. # 19 please help to solve

Answer 1

Your answer:
$y^{2} - y$
because When you combine like terms you need to find the same variable and the same exponent. The coefficients are the ones that combine. The parenthesis cannot be solved inside so just remove them. Combine the like terms.
$- 3 {y}^{2} - 7y - 9 - ( + 4 {y}^{2} + 6y + 9$
Start by combining
$- 3 {y}^{2} + 4 {y}^{2}$
which equals 1.
${y}^{2} - 7y - 9 - ( + 6y + 9$
combine ,
$- 7y + 6y$
then you will end up with
${y}^{2} - y - 9 + 9$
9 and 9 cancel out so you end up with
${y}^{2} - y$

D. is your answer

Answer 2

(−3y^2−7y−9)−(4y^2+6y+9). To solve this you must:
Distribute the negative sign like this:     
      =−3y^2−7y−9+−1(4y^2+6y+9)
=−3y^2+−7y+−9+−1(4y^2)+−1(6y)+(−1)(9) 
    =−3y^2+−7y+−9+−4y^2+−6y+−9
Then combine Like Terms: 
    =−3y^2+−7y+−9+−4y^2+−6y+−9 
  =(−3y^2+−4y^2)+(−7y+−6y)+(−9+−9)         
               =−7y^2+−13y+−18
So you would get an answer of −7y^2−13y−18.
 Hope this helped!