
已知:a/b=c/d,求证:(2a+3b)/(a+b)=(2c+3d)/(c+d)
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设 a/b=c/d = k
则 a = bk, c = dk
代入到所要证明的式子中
左 =(2a+3b)/(a+b)
= (2bk + 3b)/(bk +b)
= (2k+3)/(k+1)
右=(2c+3d)/(c+d)
= (2dk + 3d)/(dk + d)
= (2k+3)/(k+1)
所以 左 = 右
命题成立。
则 a = bk, c = dk
代入到所要证明的式子中
左 =(2a+3b)/(a+b)
= (2bk + 3b)/(bk +b)
= (2k+3)/(k+1)
右=(2c+3d)/(c+d)
= (2dk + 3d)/(dk + d)
= (2k+3)/(k+1)
所以 左 = 右
命题成立。
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