a, \(5 \left(\right. x + 2 y \left.\right) - 15 x \left(\right. x + 2 y \left.\right)\). c,(3x−2)3−3(x−4)(x+4)+(x−3)3−(x+1)(x2−x+1)

=27x^3−66x^2+63x+12

=(x+2y)(5−15x)

=5(1−3x)(x+2y)

b,4x2−12x+9

=(2x−3)^2

My favorite hobby is swimming. I started swimming when I was about seven years old. At first, I learned it with my father, and then I continued practicing by myself. I usually go swimming at the local pool near my house, especially in the summer or on weekends. Sometimes I swim with my friends, and we have a lot of fun together. Swimming not only helps me stay healthy and strong but also makes me feel relaxed after studying. I think swimming is a wonderful hobby because it improves my fitness, gives me energy, and makes my life more enjoyable