a. (x2+2x+3)+(3x2−5x+1) = 4x2−3x+4
b. (4x3−2x2−6)−(x3−7x2+x−5) = 3x3+5x2+x−1
c. −3x2(6x2−8x+1) = −18x4+24x3−3x2
d. (4x2+2x+1)(2x−1) = (4x2+2x+1)(2x−1)