Question

$(2x+3) ^{3} -8x-12=(2x+1)(2x+3)(2x+5)$

Answer 1

(2x+3)(2x+3)² -8x -12= (4x²+ 6x+2x+3)(2x+5)
(2x+3)(4x²+12x+9) -8x -12= (4x²+8x+3)(2x+5)
8x³+24x²+18x+12x²+36x+27 -8x -12= 8x³+16x²+6x +20x²+40x +15

8x³+36x²+ 54x-8x +15= 8x³ +36x² +46x +15
8x³+36x +46x+15=8x³ +36x² +46x +15