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a, \(\frac{2x3x4x5}{3x4x5x6}\)= \(\frac{2}{6}\)=\(\frac{1}{3}\)
b, \(\frac{9x8x5}{6x4x15}\)=\(\frac{3x3x4x2x5}{2x3x4x3x5}\)=1
9 x 8 x 5 / 6 x 4 x 15 = 9 x 4 x 2 x 5 / 6 x 4 x 3x 5 = 9 x 2 / 6 x 3 = 3 x 3 /2 x 3=3/2
= \(\frac{3x3x4x4x5}{3x2x4x5x3}=\frac{4x5}{2}=\frac{20}{2}=10\)
Tính nhanh:
a, 54 * 113 *45 +113
= 113 x 54 x 45 + 113 x 1
= 113 x 2430 + 113 x 1
= 113 x ( 2430 + 1 )
= 113 x 2431
= 274703.
b, 24 * 3 - 12 *5
= 12 x 2 x 3 - 12 x 5
= 12 x 6 - 12 x 5
= 12 x ( 6 - 5 )
= 12 x 1
= 12.
c, (145 * 99 + 145) - (143 *101 -143)
= ( 145 x 99 + 145 x 1 ) - ( 143 x 101 - 143 x 1 )
= 145 x ( 99 + 1 ) - 143 x ( 101 - 1 )
= 145 x 100 - 143 x 100
= 14500 - 14300
= 200.
54 x 113 x 45 + 133
=113 x 54 x 45 + 113 x 1
=113 x 2340 + 113 x 1
=113 x (2340 +1)
=113 x 2431
=274703
chúc bạn học good
\(A=\frac{10}{1\cdot2}+\frac{10}{2\cdot3}+\frac{10}{3\cdot4}+...+\frac{10}{98\cdot99}+\frac{10}{99\cdot100}\)
\(A=\frac{10}{1}-\frac{10}{2}+\frac{10}{2}-\frac{10}{3}+\frac{10}{3}-\frac{10}{4}+...+\frac{10}{99}-\frac{10}{100}\)
\(A=\frac{10}{1}-\frac{10}{100}\)
\(A=\frac{99}{10}\)
Không chắc nhá
\(A=\frac{10}{1\cdot2}+\frac{10}{2\cdot3}+\frac{10}{3\cdot4}+....+\frac{10}{98\cdot99}+\frac{10}{99\cdot100}\)
\(A=10\left(\frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+...+\frac{1}{98\cdot99}+\frac{1}{99\cdot100}\right)\)
\(A=10\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{99}-\frac{1}{100}\right)\)
\(A=10\left(1-\frac{1}{100}\right)=10\cdot\frac{99}{100}=\frac{99}{10}\)
A = 10/1x2 + 10/2x3 + 10/3x4 +........ + 10/98x99 + 10/99x100
A=10x(1/1x2+1/2x3+1/3x4+..+1/98x99+1/99x100)
A= 10x( 1-1/2+1/2-1/3+1/3-1/4+..+1/99-1/100)
A=10x( 1-1/100)
A=10x99/100
A=99/10
A = đề
A=10x(1/1x2+1/2x3+1/3x4+..+1/98x99+1/99x100)
A= 10x( 1-1/2+1/2-1/3+1/3-1/4+..+1/99-1/100)
A=10x( 1-1/100)
A=10x99/100
A=99/10
Bằng 1 nhé
Các bạn ủng hộ cho tớ đê !!!!!!!!!!!!!!!!!!!!1
9 x 8 x 5 = 9 x 5 x 8
= 40 x 8
= 320
6 x 4 x 15 = 4 x 15 x 6
= 60 x 6
= 360