Câu 1:
a, Tính M =\(3\dfrac{1}{417}\cdot\dfrac{1}{762}-\dfrac{1}{139}\cdot4\dfrac{761}{762}-\dfrac{4}{417\cdot762}+\dfrac{5}{139}\)
b, Tính \(\left(\dfrac{3}{4}-81\right)\left(\dfrac{3^2}{5}-81\right)\left(\dfrac{3^3}{6}-81\right)...\left(\dfrac{3^{2000}}{2003}-81\right)\)
Câu 2: Cho \(\left(a+3\right)\left(b-4\right)-\left(a-3\right)\left(b+4\right)=0\) . Chứng minh \(\dfrac{a}{3}=\dfrac{b}{4}\).
Câu 2
(a+3)(b-4)-(a-3)(b+4)=0
=>ab-4a+3b-12-ab-4a+3b+12=0
=>-8a=-6b
=>a/b=3/4
=>a/3=b/4
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