Tính nhanh : (18.123+9.436.2+3.5310.6):(1+7+....+100-4100)
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Ta có:
+) \(1+4+7+...+100=\left(1+100\right)+\left(4+97\right)+...+\left(49+52\right)\)(34 cặp)
\(=101.34=3434\)
+) \(3434-410=3024\)
+) \(\left(18.123+9.436.2+3.5310.6\right)=18\left(123+436+5310\right)\)
\(=18.5869=105642\)
Vậy \(A=105642:3024\approx34,93\)
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Trả lời:
Phân tích: (18.123+9.436.2−3.3510.6)=18.123+18.436−18.5310(18.123+9.436.2−3.3510.6)=18.123+18.436−18.5310⇔18.(123+436−3510)⇔18.(123+436−3510)( chung số 18 )
⇔18.(−4751)=−85518⇔18.(−4751)=−85518
Tiếp tục phân tích vế sau:
(1+4+7+...+100−410)=[(100−1):3+1].(100+1)2−410(1+4+7+...+100−410)=[(100−1):3+1].(100+1)2−410⇔1717−410=1307⇔1717−410=1307
⇔−85518:1717=−855181717⇔−85518:1717=−855181717
Vậy (18.123 + 9.436.2 + 3.5310.6 ) : ( 1 + 4 + 7 + ....... + 100 - 410 )=−855181717
~Học tốt!~