(5y2-4y)+ (2Y2+6Y-9)

(5y2-4y)+ (2Y2+6Y-9)

7y^2 + 2y - 9

To simplify the expression (5y^2-4y)+(2y^2+6y-9), you need to combine like terms. Like terms have the same variable and exponent.

First, let's combine the terms with a y^2:

5y^2 + 2y^2 = (5+2)y^2 = 7y^2

Next, let's combine the y terms:

-4y + 6y = (-4+6)y = 2y

Finally, combine the constants:

-9 remains as it is.

Putting it all together, the simplified expression is:
7y^2 + 2y - 9