1. = 4²+2×4a+a² = 16+8a+a²
2. = (2x^4)³-2×2x^4×3+3² = 4x^8 -12x^4+9
3. = (3(3b+2a))² = (9b+6a)² = 81b²+108ab+36a²
4. = -3((2-x)²-6) = -3(4-4x+x²-6) = -3(-2-4x+x²)
5. = (3y)³ = 27y³
6. = 25+10y+y²+y²-7y = 25+3y+2y²
7. = (3b-(a-3b))×(3b+a-3b) = (3b-a+3b)a = (6b-a)a