a. 12x2.65x3
= 12.65.x2+3
= 35x5
b. y2(57−2y2+0.25)
= 57y2+3−2y2+2+0,25y
= y2(57−2y2+0.25)
c. (2x2+x+4)(x2−x−1)
= 2x4−2x3−2x2+x3−x2−x+4x2−4x−4
= (2x2+x+4)(x2−x−1)
d. (3x−4)(2x+1)−(x−2)(6x+3)
= 6x2−8x+3x−4−6x2+12x−3x+6
= (3x−4)(2x+1)−(x−2)(6x+3)