若a=2,b=1/20 ,求ba²-5a(-a+b+1)+4a(3a+2),先化简,再求值.
问题描述:
若a=2,b=1/20 ,求ba²-5a(-a+b+1)+4a(3a+2),先化简,再求值.
答
ba²-5a(-a+b+1)+4a(3a+2)
=ba²+5a²-5ab-5a+12a²+8a
=ba²+17a²-5ab+3a
代入a=2,b=1/20
=4/20+20-1/2+6
=25.7