Simplify the following expressions.
(Please don't answer for the points or I will be reporting you)
a. 4xy + 7x^2 − 7y^2 + 9xy − 8y^2 + 8x^2
b. (14x^2 − 2x + 5) + (−6x^2 + 8x − 5)
c. (5y − 3xy + 7x^2) − (8xy − 6 + 2x^2)
d. (6x^2 − 2x + 7) + (−2x^2 + 9x + 5) − (x2 + 7x − 8)
e. (7x^4 − 5x − 3) + (6x^2 + 9x^4 − 2x^3) − (4x^4 + 3x^2 − 2x^2 + x + 1)