1)(5a-12b)(5a+12b)= (5a-12b)*5a+(5a-12b)*12b= 25a²-60ab+60ab-144b²=25a-144b²
2)(6а+5b)²= 6²a²+5²b²
3)(8a-b)²=8²a²-b²
4)(а + 3)(а² - 3а +9)= (а+3)*a²+(a+3)*(-3a)+(a+3)*9=a³+3a²-3a²-9a+9a+27=a³+27
5) (b - 2)(b²+ 2b +4)=(b-2)*b²+(b-2)*2b+(b-2)*4=b³-2b²+2b³+4b+4b-8=3b³-2b²+8b
6.(- a² + 9)(a² + 9)=(-a²+9)*a²+(-a²+9)*9=-a⁴+9a²-9a+81=-a⁴+81