1. a) (x²+2y)(x²+2y)-(x²-2y)(x²+2y) = (x²+2y)²-(x⁴-4y²) = x⁴+4x²y+4y²-x⁴+4y² = 4x²y+8y²

б) (3a-b²)(3a+b²)+(3a-b²)(3a-b²) = 9a²-b⁴+(3a-b²)² = 9a²-b⁴+9a²-6ab²+b⁴= 18a²-6ab²

2. a) (x²+b)(x²+2b) = x⁴+2bx²+bx²+2b²= x⁴+3bx²+2b²

б) (2m+n²)(2n-m²) = 4mn-2m³+2n³-n²m²

3. a)(5b³)×(3b²x)=15b⁵x

б)5(3mn)×(6m)=15mn×6m=90m²n

в)(5x²y)×(-xy)= -5x³y²

г)(2,5m)×(3mn²)=7,5m²n²