Đáp án:
`a,236`
`b,3`
`c,144`
Giải thích các bước giải:
`a) 26 + 27 + ... + 33`
`= (26 + 33) + (27 + 32) + (28 + 31) + (29 + 30)`
`= 59 + 59 + 59 + 59`
`= 236`
`b) ( 2^20 . 13 + 2^10 . 65 ) / ( 2^8 . 104 )`
`= ( 2^20 . 78 ) / ( 2^8 . 104 )`
`= ( 2^{2}.2^{18} . 78 ) / 104`
`=(2^{18}.4.78)/(104)`
`=(2^{18}.312)/104`
`= 3.2^{18}`
`c)12+13+..+20`
`=12+18+13+17+14+16+15+20+19`
`=30+30+30+35+19`
`=90+19+35`
`=109+35`
`=144`