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2A=\(\frac{2}{1.2.3}\)+\(\frac{2}{2.3.4}\)+...+\(\frac{2}{18.19.20}\)
=1/1.2-1/2.3+1/2.3-1/3.4+...+1/18.19-1/19.20
=1/2-1/19.20
A=1/4-1/19.20.2
vậy A<1/4
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35 x 36 + 36 x 63 + 36 : 1/2
= 35 x 36 + 36 x 63 + 36 x 2
= 36 x ( 35 + 63 + 2 )
= 36 x 100
= 3 600
/HT\
=35x36+36x63+36x2 (nếu bn ko hiểu tại sao mik nhân 2 thì: 36 : 1/2 = 36 x 2/1= 36 x2) =35x(35+63+2) = 35x100=3500
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a) \(...=16.\left(36-37\right)=16.\left(-1\right)=-16\)
b) \(...=9.3+9.50=9.\left(3+50\right)=9.53=477\)
c) \(...=2.\left(\left(5.16-18\right)+36:18\right)=2.\left(70+2\right)=2.72=144\)
d) \(...=5\left(48:8+44\right)=5\left(6+44\right)=5.50=250\)
e) \(...=20-6=14\)
f) \(...=50+13-2=61\)
a) 16 . 36 - 16 . 37
= 16 . (36 - 37)
= 16 . (-1)
= -16
b) 36 : 4 . 3 + 9 . 50
= 9 . 3 + 9 . 50
= 9 . (3 + 50)
= 9 . 53
= 477
c) 2 . (5 . 16 - 18) + 36 : 18 . 2
= 2 . (80 - 18) + 2 . 2
= 2 . 62 + 2 . 2
= 2 . (62 + 2)
= 2 . 64
= 128
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\(x^2-\left(-\frac{5}{36}\right)=\frac{14}{36}\)
\(x^2+\frac{5}{36}=\frac{14}{36}\)
\(x^2=\frac{14}{36}-\frac{5}{36}\)
\(x^2=\frac{1}{4}\)
\(\Rightarrow x\in\left\{\frac{-1}{2};\frac{1}{2};\frac{1}{-2};\frac{-1}{-2}\right\}\)
Vậy \(x\in\left\{\frac{-1}{2};\frac{1}{2};\frac{1}{-2};\frac{-1}{-2}\right\}\)
\(x^2-\left(\frac{-5}{36}\right)=\frac{14}{36}\Rightarrow x^2=\frac{14}{36}+\left(\frac{-5}{36}\right)=\frac{14}{36}-\frac{5}{36}=\frac{9}{36}=\frac{1}{4}\)
\(\Rightarrow x^2=\frac{1}{4}\Rightarrow x^2=\pm\left(\frac{1}{2}\right)^2\)
vậy x = \(\frac{1}{2}\) hoặc x = \(\frac{-1}{2}\)
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Cách 1
\(2\dfrac{3}{4}\)+ \(5\dfrac{7}{9}\)= \(\dfrac{11}{4}+\dfrac{47}{9}\)
= \(\dfrac{99}{36}+\dfrac{188}{36}\)
= \(\dfrac{287}{36}\)= 7,9722...
Cách 2
\(2\dfrac{3}{4}+5\dfrac{7}{8}=2\dfrac{55}{36}+5\dfrac{55}{36}\)
= \(7\dfrac{55}{36}=8\dfrac{19}{36}\)
Cách 1 mình làm nhầm bài đúng phải là
\(2\dfrac{3}{4}+5\dfrac{7}{9}=\dfrac{11}{4}+\dfrac{52}{9}=\dfrac{99}{36}+\dfrac{208}{36}\)
=\(\dfrac{307}{36}\)=8,527777778
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\(0,36\cdot4+36\%+2+2\cdot4\cdot0,18\)
\(=0,36\cdot4+0,18\cdot8+0,36+2\)
\(=0,36\cdot5+0,36\cdot4+2\)
\(=0,36\cdot9+2=2+3,24=5,24\)
Sửa đề:\(0,36\times4+36\%\times2+2\times4\times0,18\)
\(=0,36\times4+0,36\times2+4\times0,36\)
\(=0,36\times\left(4+4+2\right)\)
\(=0,36\times10\)
\(=3,6\)