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a)
Ta có : ( 1 + 2 + 3 + ... + 99)
Số số hạng là: ( 99 - 1 ) : 1 + 1 = 100
Tổng là: ( 99 + 1 ) x 100 : 2 = 5000
=> 5000 x ( 13 - 12 - 1 ) x 15
=> 5000 x 10 x 15
=> 50000 x 15
=> 750000
Ko muốn vt nx :))
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`a)25xx532xx4`
`=(25xx4)xx432`
`=432xx100=43200`
`b)456xx200-456xx100`
`=456xx(200-100)`
`=456xx100=45600`
\(a,25\times432\times4=25\times4\times432=100\times432=4320\\ b,456\times200-456\times100=456\times\left(200-100\right)=456\times100=45600\)
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B=1+2-(3+4)+5+6-..-100+101
B=(3+11+19+...+195)-(7+15+...+199)+101
B=25.99-25.103+101
B=-100+101=1
Vậy B=1
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\(\text{[ 1 + 2 + 3 +4 + ........ + 999 + 1000 +1001 ] x [ [ 456 x 9 + 456 ] : [4570 -10 ] ] }\)
\(=\left[\frac{1001+1}{2}\right].\)\(\left[456.\left(9+1\right):4560\right]\)
\(=501.1\)
\(=501\)
chúc bạn học tốt
1/2 : 4/5 x 456 -98
= 5/8 x 456 - 98
= 285 - 98
= 187
1/2:4/5 x 456-98
=5/8 x 456 -98
=285 - 98
=187