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(2020+27) - [ 2020 + (-73) ] - 129
= 2047 - 1947 - 129
= 100 - 129 = -29
BÀi 1:
a: (-243+345)-(257+(-55)-129)
=-243+345-257+55+129
=(-243-257)+(345+55)+129
=-500+400+129
=-100+129
=29
b: \(\left(-2\right)^3-45:\left(-3\right)^2-\left(-2019\right)^0\cdot\left(-1\right)^{2019}\)
\(=-8-\frac{45}{9}-1\cdot\left(-1\right)\)
=-8-5+1
=-13+1
=-12
c: \(\left\lbrack27\cdot\left(-67\right)+33\cdot\left(-27\right)\right\rbrack:\left(-30\right)\)
\(=\frac{-27\left(67+33\right)}{-30}\)
\(=\frac{9}{10}\cdot100=90\)
d: \(\left(1^2+2^2+\cdots+100^2\right)\left(3^4-9^2\right)\)
\(=\left(1^2+2^2+\cdots+100^2\right)\left(81-81\right)\)
=0
e: \(53\cdot47+53^2-2021^0\)
\(=53\left(53+47\right)-1\)
=5300-1
=5299
i: 38+(-21)+(-58)+(-6)
=(38-58)+(-21-6)
=-20-27
=-47
h: (2020+27)-[2020+(-73)]-129
=2020+27-2020+73-129
=100-129
=-29
a) $34-29+(-14)+129-(-114)$
$=34-29-14+129+114$
$=34+(129-29)+(114-14)$
$=34+100+100$
$=234$
b) $27\cdot(-35)+(-27)\cdot64-27$
$=(-27)\cdot35+(-27)\cdot64+(-27)\cdot1$
$=(-27)\cdot(35+64+1)$
$=(-27)\cdot(99+1)$
$=(-27)\cdot100$
$=-2700$
c) $160-(4\cdot5^2-3\cdot2^3)\cdot2-(-12)$
$=160-(4\cdot25-3\cdot8)\cdot2+12$
$=160-(100-24)\cdot2+12$
$=160-76\cdot2+12$
$=160-152+12$
$=160-(152-12)$
$=160-140$
$=20$
a, 34 - 29 + (-14) + 129 - (-114)
= 34 + (129 - 29) + (114 - 14)
= 34 + 100 + 100
= 234
b, 27.(-35) + (-27).64 - 27
= (-27).(35 + 64 + 1)
= - 27 . 100
= - 2700
c, 160 - (4.52 - 3.23).2 - (-12)
= 160 - (4.25 - 3.8).2 + 12
= 160 - (100 - 24).2 + 12
= 160 - 76.2 + 12
= 160 - 152 + 12
= 8 + 12
= 20
b: Sửa đề: \(B=1\cdot3+2\cdot4+3\cdot5+4\cdot6+\cdots+2018\cdot2020\)
\(=1\left(1+2\right)+2\left(2+2\right)+\cdots+2018\left(2018+2\right)\)
\(=\left(1^2+2^2+\cdots+2018^2\right)+2\left(1+2+\cdots+2018\right)\)
\(=\frac{2018\left(2018+1\right)\left(2\cdot2018+1\right)}{6}+2\cdot\frac{2018\cdot2019}{2}\)
\(=\frac{2018\cdot2019\cdot4037}{6}+2018\cdot2019=1009\cdot673\cdot4037+2018\cdot2019\)
\(=1009\cdot673\left(4037+2\cdot3\right)=1009\cdot673\cdot4043\)
=2745427451
c: Ta có: \(C=\left(1+2+3+\cdots+2020\right)\left(20192019\cdot2020-2019\cdot20202020\right)+\left(15-12\right)^2\)
\(=\frac{2020\left(2020+1\right)}{2}\cdot2019\cdot2020\cdot\left(10001-10001\right)+3^2\)
=0+9
=9
b: Sửa đề: \(B=1\cdot3+2\cdot4+3\cdot5+4\cdot6+\cdots+2018\cdot2020\)
\(=1\left(1+2\right)+2\left(2+2\right)+\cdots+2018\left(2018+2\right)\)
\(=\left(1^2+2^2+\cdots+2018^2\right)+2\left(1+2+\cdots+2018\right)\)
\(=\frac{2018\left(2018+1\right)\left(2\cdot2018+1\right)}{6}+2\cdot\frac{2018\cdot2019}{2}\)
\(=\frac{2018\cdot2019\cdot4037}{6}+2018\cdot2019=1009\cdot673\cdot4037+2018\cdot2019\)
\(=1009\cdot673\left(4037+2\cdot3\right)=1009\cdot673\cdot4043\)
=2745427451
c: Ta có: \(C=\left(1+2+3+\cdots+2020\right)\left(20192019\cdot2020-2019\cdot20202020\right)+\left(15-12\right)^2\)
\(=\frac{2020\left(2020+1\right)}{2}\cdot2019\cdot2020\cdot\left(10001-10001\right)+3^2\)
=0+9
=9
(-12) + (-18)
= -30
------------------
(-90) + 27 + (-10) + 73
= [(-90) + (-10) + (27 + 73)
= -100 + 100
= 0
---------------------------------
25 . (-5) . (-4)
= 25 . (-4) . (-5)
= -100 . (-5)
= 100 . 5
= 500
----------------------------------------
(-15) . 40 : 6
= [(-15) . 40] : 6
= (-600) : 6
= -100
-----------------------------------
(-27) . 58 + (-27) . 42
= (-27) . (58 + 42)
= (-27) . 100
= -2700
À câu này giải theo cách này e nhé!
E tham khảo nha:(-- được xem là +)
=>(2020+27)+(2020-73)-129
=2047+1947-129=3865