Question

Punctul b .
Vă rog ,dau 50 de puncte + coroana . Este urgent !!
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Answer 1

Răspuns:

Explicație pas cu pas:

2/1*3 = 1 - 1/3

2/3*5 = 1/3 - 1/5

......

2/39*41 = 1/39 - 1/41

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2/1*3 + 2/3*5 + ...+ 2/39*41 = 1 - 1/3 + 1/3 - 1/5 + ... + 1/39 - 1/41

= 1 - 1/41 = 41/41 - 1/41 = 40/41

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3/1*4 = 1 - 1/4

3/4*7 = 1/4 - 1/7

......................

3/37*40 = 1/37 - 1/40

................................

3/1*4 + 3/4*7 + ...+ 3/37*40 = 1 - 1/4 + 1/4 - 1/7 + ....+ 1/37 - 1/40

= 1 - 1/40 = 40/40 = 1/40 = 39/40

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40/41 - 39/40 = 40*40/40*41 - 39*41/40*41 = (1600 - 1599)/40*41 = 1/40*41

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80*82/40*41 = 4

x = √4 = 2