已知25a2-10a+1+|4b+1|=0,求[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b).
题目
已知25a2-10a+1+|4b+1|=0,求[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b).
答案
∵25a
2-10a+1+|4b+1|=0,∴(5a-1)
2+|4b+1|=0,
∴a=
、b=
−∴[(4a+3b)(4a-3b)-(2a-5b)(8a+5b)]÷(-2b)
=(16a
2-9b
2-16a
2+25b
2+30ab)÷(-2b)
=(16b
2+30ab)÷(-2b)
=-8b-15a
=-8×(-
)-15×
=2-3
=-1.
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