Verified answer

(9a^(2)-2a-5)-(-9a^(2)+2a+5)

Multiply -1 by each term inside the parentheses.

9a^(2)-2a-5+9a^(2)-2a-5

Since 9a^(2) and 9a^(2) are like terms, add 9a^(2) to 9a^(2) to get 18a^(2).

18a^(2)-2a-5-2a-5

Since -2a and -2a are like terms, subtract 2a from -2a to get -4a.

18a^(2)-4a-5-5

Subtract 5 from -5 to get -10.

18a^(2)-4a-10

It would be tempting to put zero, but you have to observe the question in pieces.

(9a^2-2a-5)-(-9a^2+2a+5)

since this is set up in like terms, break it up into like terms

(+9a^2)-(-9a^2)

(-2a)-(+2a)

(-5)-(+5)

keeping in mind that subtracting a negative is the same as adding, and you leave variables and exponents alone you get:

18a^2

-4a

-10

combining these together again you get:

18a^2-4a-10

is 5