5ab-{2a的2次方b-[3abc-(4ab的2次方-a的2次方b)]}
问题描述：
5ab-{2a的2次方b-[3abc-(4ab的2次方-a的2次方b)]}
15a的2次方-{-4a的2次方+[5a-8a的2次方-(2a的2次方-a)+9a的2次方]-3a}
其中a=-5分之1
答
5ab-{2a^2b-[3abc-(4ab^2-a^2b)]}
=5ab-{2a^2b-[3abc-4ab^2+a^2b]}
=5ab-{2a^2b-3abc+4ab^2-a^2b}
=5ab-{a^2b-3abc+4ab^2-a^2b}
=5ab-a^2b+3abc-4ab^2+a^2b
=5ab+3abc-4ab^2
15a^2-{-4a^2+[5a-8a^2-(2a^2-a)+9a^2]-3a}
=15a^2-{-4a^2+[5a-8a^2-2a^2+a+9a^2]-3a}
=15a^2-{-4a^2+6a-a^2-3a}
=15a^2+5a^2-3a
=20a^2-3a
=20(-1/5)^2-3(-1/5)
=4/5+3/5
=7/5
=1.4