已知25a2-10a+1+|4b+1|=0,求[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b)
1个回答

解题思路:由25a2-10a+1+|4b+1|=0可求得a、b的值,化简[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b),再代入计算即可.

∵25a2-10a+1+|4b+1|=0,∴(5a-1)2+|4b+1|=0,

∴a=[1/5]、b=−

1

4

∴[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b)

=(16a2-9b2-16a2+25b2+30ab)÷(-2b)

=(16b2+30ab)÷(-2b)

=-8b-15a

=-8×(-[1/4])-15×[1/5]

=2-3

=-1.

点评:

本题考点: 整式的加减—化简求值;非负数的性质:绝对值;非负数的性质:偶次方.

考点点评: 本题利用方程25a2-10a+1+|4b+1|=0的特殊解法,解得a、b的值,从而使问题变的简单.