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a) 21x72-11x72+90x72+49x125x16
= 21 x 49 - 11 x 49 + 90 x 49 + 49 x 125 x 16
= 49 x ( 21 - 11 + 90 + 125 x 16 )
= 49 x ( 21 - 11 + 90 + 2000 )
= 49 x 2100
= ( 50 - 1 ) x 2100
= 50 x 2100 - 2100
= 105 000 - 2100
= 102 900
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\(21.7^2-11.7^2+90.7^2+49.125.16\)
\(=7^2.\left(21-11+90+49.16\right)\)
\(=...............................................\)
nha nguyenvankhoi196a
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\(S=5^{16}+4.5^{15}+7^{16}+11.7^{15}\)5
\(S=5^{15}.5+4.5^{15}+7^{15}.5+11.7^{15}\)
\(S=5^{15}.\left(5+4\right)+7^{15}.\left(11+5\right)\)
\(S=5^{15}.9+7^{15}.16\)
S không chia hết cho 9 vì 16 không chia hết cho 9
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29-28-27-26-25-24-23-22-21-20
= 28-27-26-25-24-23-22-21-20
= 27-26-25-24-23-22-21-20
= 26-25-24-23-22-21-20
= 25-24-23-22-21-20
= 24-23-22-21-20
= 23-22-21-20
= 22-21-20
= 21-20
= 2 - 1
= 1
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Ta có: 12 + 22 + 32 + ..... + 992 + 1002 = 338350
=> 22.(12 + 22 + 32 + ..... + 992 + 1002) = 22 . 338350
=> 22 + 42 + 62 +.....+ 1982 + 2002 = 4.338350
=> 22 + 42 + 62 +.....+ 1982 + 2002 = 1 353 400
Ta có: 12 + 22 + 32 + ..... + 992 + 1002 = 338350
=> 22.(12 + 22 + 32 + ..... + 992 + 1002) = 22 . 338350
=> 22 + 42 + 62 +.....+ 1982 + 2002 = 4.338350
=> 22 + 42 + 62 +.....+ 1982 + 2002 = 1 353 400
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1.
2^3 . 4^4 . 16^2
= 2^3 . 2^8 . 2^8
= 2^19
2.
8^6 : 2^3
= 2^18 : 2^3
= 2^15
Mấy câu kia tương tự thôi :D
1) 23.46.162=23.(22)6.(24)2=23.212.28= 223
2) 86 : 23 = (23)6 : 23 = 218 : 23 = 215
3) 273:33 =(33)3 : 33 = 39 : 33 = 36
4) 153 : 53 = (3.5)3 : 53 = 33
mk nghĩ là 9 800 000
ah nhầm 102 900