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1) 12 x 19 + (3 x 4) x 24 - (6 x 2) x 33
= 12 x19 + 12 x 24 -12 x 33
= 12 x (19 + 24 - 33)
= 12 x 10
=120
2) 35 x1001-35
=35 x (1001 - 1)
= 35 x 1000
= 35 000
1) 12 x 19 + (3 x 4) x 24 - (6 x 2) x 33
= 12 x19 + 12 x 24 -12 x 33
= 12 x (19 + 24 - 33)
= 12 x 10
=120
2) 35 x1001-35
=35 x (1001 - 1)
= 35 x 1000
= 35 000
(-4).8.25.(-125).7
=[(-4x.25]x[8.(-125)]
=-100 x -1000
=100000
áp dụng quy tắc đổi dấu
b) 35-19+2019-35-2019=-19+[(35-35)-(2019-2019)]
=-19+0+=-19
a) \(124+\left(-56\right).124+\left(-124\right)\left(-47\right)=124.1-56.124+124.47\)
\(=124.\left(1-56+47\right)=124.\left(-8\right)=-992\)
b) \(35-19+2019-35+\left(-2019\right)=35-19+2019-35-2019\)
\(=\left(35-35\right)+\left(2019-2019\right)-19=0+0-19=0-19=-19\)
c) \(345-150\div\left[\left(3^3-24\right)^2-\left(-21\right)\right]+2020^0\)
\(=345-150\div\left[\left(27-24\right)^2+21\right]+1=345-150\div\left(3^2+21\right)+1\)
\(=345-150\div24+1=345-6,25+1=339,75\)
\(123\times35+124\times65\)
\(=123\times35+\left(123+1\right)\times65\)
\(=123\times35+123\times65+65\)
\(=123\times\left(35+65\right)+65\)
\(=123\times100+65\)
\(=12300+65\)
\(=12365\)
123 x 35 + 124 x 65
= 123 x 35 + 123 x 65 + 65
= 123 x (35 + 65) + 65
= 123 x 100 + 65
= 12300 + 65
= 12365
e) 2+4+6+8....+24
số hạng
(24-2):2+1=10
tổng
(24+2)x10:2=130
đ\s....
A= \(\frac{1}{3}+\frac{1}{8}+\frac{1}{15}+\frac{1}{24}+\frac{1}{35}+\frac{1}{48}+\frac{1}{63}+\frac{1}{80}\)
A= \(\frac{2}{2}.\left(\frac{1}{1.3}+\frac{1}{2.4}+\frac{1}{3.5}+\frac{1}{4.6}+\frac{1}{5.7}+\frac{1}{6.8}+\frac{1}{7.9}+\frac{1}{8.10}\right)\)
A=\(\frac{1}{2}.\left(\frac{2}{1.3}+\frac{2}{3.5}+\frac{2}{5.7}+\frac{2}{7.9}+\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}\right)\)
\(A=\frac{1}{2}.\left(\frac{1}{1}-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+\frac{1}{7}-\frac{1}{9}+\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}\right)\)
\(A=\frac{1}{2}.\left(1-\frac{1}{9}+\frac{1}{2}-\frac{1}{10}\right)\)
A= tự tính
1. Mẫu số chung là 3x4x5=60
1/3 = 1x4x5/60 = 20/60
2/4 = 2x3x5 = 30/60
4/5 = 4x3x4 = 48/60
2. Tính nhanh 35x26+35x27+70/(35+35+...+35)
= 35x(26+27)+35x2/35x100
=35x53+1/50
=(35x53x50+1)/50
= 92751/50
\(\left(-35\right).124-\left(-35\right).24+1500\)
\(=35.\left(-124\right)+35.24+1500\)
\(=35.\left(-124+24\right)+1500\)
\(=35.\left(-100\right)+1500\)
\(=-3500+1500=-2000\)