a. −2x2+6x2 = (−2+6)x2 = 4x2
b. 4x3−8x3 = (4−8)x3 = −4x3
c. 3x4(−6x2) = 3.(−6).x4+2 = −18x6
d. (−24x6):(−4x3) = (−24:6)x6−3 = 6x3
