Respuesta :

Jonathank
(-5y^3 - 7y) + (7y^3 + 8y +9)


-5y^3+7y^3-7y+8y+9   <---- Group like terms
 
-5y^3+7y^3+y+9  <---- Add similar elements 

Answer: 2y^3+y+9

Read it carefully as it may look confusing with the symbols.