х²-(16b²-8bc+c²)=x²-(4b-c)²=
(x-4b+c)(x+4b-c) - это ответ.
1)7(х+3х)=224
7х+21х=224
28х=224
х=8
2)9х+7(х+9)=287
9х+7х+63=287
16х+63=287
16х=287-63
16х=224
х=14
1 - 13/55 = 55/55 - 13/55 = 42/55
6 - 9/20 = 5 20/20 - 9/20 = 5 11/20
10 - 5 12/35 = 9 35/35 - 5 12/35 = 4 23/35
8 - 4 5/22 = 7 22/22 - 4 5/22 = 3 17/22