Question

A=3/4.9 3/9.14 3/14.19 ... 3/154.159

Answer 1

ở phần cách là dấu gì vậy bạn?

Answer 2

 

\(A=\dfrac{3}{4\cdot9}+\dfrac{3}{9\cdot14}+\dfrac{3}{14\cdot19}+...+\dfrac{3}{154\cdot159}\) đề ntn phải ko ạ?

\(\dfrac{5}{3}A=\dfrac{5}{4\cdot9}+\dfrac{5}{9\cdot14}+\dfrac{5}{14\cdot19}+...+\dfrac{5}{154\cdot159}\)

\(\dfrac{5}{3}A=\dfrac{1}{4}-\dfrac{1}{9}+\dfrac{1}{9}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{19}+...+\dfrac{1}{154}-\dfrac{1}{159}\)

\(\dfrac{5}{3}A=\dfrac{1}{4}-\dfrac{1}{159}\)

\(\dfrac{5}{3}A=\dfrac{155}{636}\\ A=\dfrac{31}{212}\)

Answer 3

53A=14−19+19−114+114−119+...+1154−115953�=14−19+19−114+114−119+...+1154−1159

53A=155636A=3121253�=155636�=31212

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53A=14−19+19−114+114−119+...+1154−115953�=14−19+19−114+114−119+...+1154−1159

53A=155636A=3121253�=155636�=31212

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