a)64c²-k⁴=(8c)²-(k²)²=(8c-k²)(8c+k²).
b)(2dy+5)²=(2dy)²+2×2dy×5+5²=4d²y²+20dy+25.
c)27n³-125m³=(5m-3n)(5m²+5m×3n+3n³).
a)64c²-k⁴=(8c)²-(k²)²=(8c-k²)(8c+k²).
b)(2dy+5)²=(2dy)²+2×2dy×5+5²=4d²y²+20dy+25.
c)27n³-125m³=(5m-3n)(5m²+5m×3n+3n³).