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.