29.5/2.35
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\(x-\dfrac{12}{8\cdot11}-\dfrac{12}{11\cdot14}-\dfrac{12}{14\cdot17}-...-\dfrac{12}{32\cdot35}=\dfrac{43}{70}\) (phải là `32*35` chứ nhỉ?)
\(x-\left(\dfrac{12}{8\cdot11}+\dfrac{12}{11\cdot14}+\dfrac{12}{14\cdot17}+...+\dfrac{12}{32\cdot35}\right)=\dfrac{43}{70}\)
\(x-4\left(\dfrac{3}{8\cdot11}+\dfrac{3}{11\cdot14}+\dfrac{3}{14\cdot17}+...+\dfrac{3}{32\cdot35}\right)=\dfrac{43}{70}\)
\(x-4\left(\dfrac{1}{8}-\dfrac{1}{11}+\dfrac{1}{11}-\dfrac{1}{14}+\dfrac{1}{14}-\dfrac{1}{17}+...+\dfrac{1}{32}-\dfrac{1}{35}\right)=\dfrac{43}{70}\)
\(x-4\left(\dfrac{1}{8}-\dfrac{1}{35}\right)=\dfrac{43}{70}\\ x-4\cdot\dfrac{27}{280}=\dfrac{43}{70}\)
\(x-\dfrac{27}{70}=\dfrac{43}{70}\\ x=\dfrac{43}{70}+\dfrac{27}{70}\\ x=\dfrac{70}{70}=1\)
Có : 7/2^2.35 = 7/2^2.5.7 = 1/2^2.5
9/2^2.3^2.10 = 3^2/2^2.3^2/10 = 1/2^2.10
Vì 2^2.5 < 2^2.10
=> 1/2^2.5 > 1/2^2.10
=> 7/2^2.35 > 9/2^2.3^2.10
Tk mk nha
45 . ( 2.x - 4 ) . 13 = 0
45 . 13 . ( 2.x - 4 ) = 0
585 . ( 2.x - 4 ) = 0
( 2.x - 4 ) = 0 : 585
2.x - 4 = 0
2.x = 0 + 4
2.x = 4
x = 4 : 2
x = 2
( x + 7 ) . 35 = 2.35
x + 7 = ( 2 . 35 ) : 35
x + 7 = 35
x = 35 - 7
x = 28
43 . ( x - 19 ) = 86
x - 19 = 86 : 43
x - 19 = 2
x = 2 + 19
x = 21
1) (x-3)(x-5) = 0
\(\Rightarrow\orbr{\begin{cases}x-3=0\\x-5=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=5\end{cases}}\)
(x+7).35 = 2.35
\(\Rightarrow x+7=2\)
\(\Rightarrow x=2-7=-5\)
Vậy x = -5
2) 1.2 + 2.3 + 3.4 + .... + 99.100
Đặt A = 1.2 + 2.3 + .... + 99.100
3A = 1.2.3 + 2.3.4 + 3.4.3 + .... + 99.100.3
3A = 1.2.(3-0) + 2.3.(4-1) + 3.4.(5-2)+ .... + 99.100.(101-98)
3A = ( 1.2.3 + 2.3.4 + 3.4.5 +.... + 99.100.101 ) - ( 0.1.2 + 1.2.3 + 2.3.4 + ... + 98.99.100 )
3A = 99.100.101 - 0.1.2
3A = 999900 - 0
3A = 999900
A = 999900 : 3
A = 333300
Vậy A = 333300
\(\frac{29.5}{2.35}=\frac{29.5}{2.5.7}=\frac{29}{2.7}=\frac{29}{14}\)
bằng 12,5531
bạn nhé