(a-b)÷(a+b) 要怎么算? (3/4-1/9)÷(3/4+1/9) =? =? =?
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(a-b)÷(a+b) 要怎么算? (3/4-1/9)÷(3/4+1/9) =? =? =?
(a-b)÷(a+b)
=(a+b-2b)÷(a+b)
=1-2b÷(a+b)
(3/4-1/9)÷(3/4+1/9)
=1-2/9÷(3/4+1/9)
=1-2/9÷31/36
=1-2/9×36/31
=1-8/31
=23/31
(a-b)÷(a+b)=(a-b)/(a+b)
没有简便方法,也没有公式
(3/4-1/9)÷(3/4+1/9)
只能先去分母了
原式=(27-4)/(27+4)=23/31
(3/4-1/9)÷(3/4+1/9)=23/31
都用平方差公式
(a-b)÷(a+b)
=[(a-b)(a-b)]÷[(a+b)(a-b)]
=(a-b)²/(a²-b²)
(3/4-1/9)÷(3/4+1/9)
=[(3/4-1/9)(3/4-1/9)]÷[(3/4+1/9)(3/4-1/9)]
=(3/4-1/9)²/[(3/4)²-(1/9)...
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都用平方差公式
(a-b)÷(a+b)
=[(a-b)(a-b)]÷[(a+b)(a-b)]
=(a-b)²/(a²-b²)
(3/4-1/9)÷(3/4+1/9)
=[(3/4-1/9)(3/4-1/9)]÷[(3/4+1/9)(3/4-1/9)]
=(3/4-1/9)²/[(3/4)²-(1/9)²]
=(3/4-1/9)²/(9/16-1/81)
=(29/36-4/36)²/(729/1296-16/1296)
=(25/36)²/(713/1296)
=(625/1296)/(713/1296)
=625/713
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