Tính nhanh
c) C=(1 – 1/2) x ( 1 - 1/3) x (1 – 1/4) x (1 – 1/5) x (1 – 1/6) x ……….. x ( 1 - 1/2015 ) x ( 1- 1/2016)
Những câu hỏi liên quan
Tính Nhanh
a) 254x399–145 / 254+399 x 253=
b) 5932+6001x5931 / 5932+6001-69
c) C=(1 – 1/2) x ( 1 - 1/3) x (1 – 1/4) x (1 – 1/5) x (1 – 1/6) x ………..
x ( 1 - 1/2015 ) x ( 1- 1/2016)
\(\frac{5932+6001x5931}{5932x6001-69}=\frac{6001x5931+5932}{5931x6001+6001-69}=\frac{6001x5931+5932}{6001x5931+5932}=1\)
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Tính (1-1/2)x(1-1/3)x(1-1/4)x( 1-1/5)x .........( 1-1/2015)x(1-1/2016)
\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)..........\left(1-\frac{1}{2016}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.........\frac{2015}{2016}\)
\(=\frac{1.2.......2015}{2.3.......2016}\)
\(=\frac{1}{2016}\)
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\(\left(1-\frac{1}{2}\right)\left(1-\frac{1}{3}\right)........\left(1-\frac{1}{2016}\right)\)
\(=\frac{1}{2}.\frac{2}{3}.......\frac{2015}{2016}=\frac{1}{2016}\)
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Tim x biet:
a.2|2x-3|=1/2
b.(x-1)^2=9/16
c.3/5(x-5/6)-1/2(3/2-1)=-1/4
d.1/3+1/6+1/10+......+2/x(x+1)=2015/2016
a) \(\Leftrightarrow\left|2x-3\right|=\frac{1}{4}\Leftrightarrow\orbr{\begin{cases}x\ge\frac{3}{2}\mid:2x-3=\frac{1}{4}\Rightarrow2x=\frac{13}{4}\Rightarrow x=\frac{13}{8}\left(TM\right)\\x< \frac{3}{2}\mid:3-2x=\frac{1}{4}\Rightarrow2x=\frac{11}{4}\Rightarrow x=\frac{11}{8}\left(TM\right)\end{cases}.}\)
b) \(\Leftrightarrow\left|x-1\right|=\frac{3}{4}\Leftrightarrow\orbr{\begin{cases}x\ge1\mid:x-1=\frac{3}{4}\Rightarrow x=\frac{7}{4}\left(TM\right)\\x< 1\mid:1-x=\frac{3}{4}=>x=\frac{1}{4}\left(TM\right)\end{cases}}\)
c) \(\frac{3}{5\left(x-\frac{5}{6}\right)}-\frac{1}{2\left(\frac{3}{2}-1\right)}=-\frac{1}{4}\Leftrightarrow\frac{3}{\frac{5\left(6x-5\right)}{6}}-\frac{1}{2\cdot\frac{1}{2}}=-\frac{1}{4}\Leftrightarrow\frac{18}{5\left(6x-5\right)}=-\frac{1}{4}+1\)
\(\Leftrightarrow\frac{18}{5\left(6x-5\right)}=\frac{3}{4}\Leftrightarrow6x-5=\frac{24}{5}\Leftrightarrow6x=\frac{49}{5}\Leftrightarrow x=\frac{49}{30}\)
d) \(\frac{1}{3}+\frac{1}{6}+\frac{1}{10}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2016}\)
\(\Leftrightarrow\frac{2}{2\cdot3}+\frac{2}{3\cdot4}+\frac{2}{4\cdot5}+...+\frac{2}{x\left(x+1\right)}=\frac{2015}{2016}\)
\(\Leftrightarrow2\cdot\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2015}{2016}\)
\(\Leftrightarrow2\left(\frac{1}{2}-\frac{1}{x+1}\right)=\frac{2015}{2016}\Leftrightarrow2\cdot\frac{x+1-2}{2\left(x+1\right)}=\frac{2015}{2016}\Leftrightarrow\frac{x-1}{x+1}=\frac{2015}{2016}\)
\(\Leftrightarrow2016x-2016=2015x+2015\Leftrightarrow x=2015+2016=4031\)
Vậy x = 4031.
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bài 7:tính
A=1-2+3-4+5-6+......+2015-2016
B=1+2-3-4+5+6+......+2013+2014-2015-2016
C=1-4-7-10-......-100
bài 8:tìm x thuộc z biết:
a,x.(x+2)=0
b,(x+2).(x-4)=0
a,
x-2/3-2/15-2/35-2/63=1/9
b
(x+1
3)+(x+1/9)+(x+1/27)+(x+1/81)=56/81
c,
(1/3*5+1/5*7+1/7*9+.....+1/19*21)*x=9/7
d,3+5+7+...+2015/2+4+6+...+2016+x=1
e,2/6+2/12+2/20+...+2/x*(x+1)=2013/2015
b1 :tính
a) N (1/2 - 1). (1/3 - 1). (1/4 - 1) .... (1/2016 - 1). (1/2017 - 1)
b) P (-1/1/2). (-1/1/3). (-1/1/4) ... (-1/1/2015). (2016/01/01)
c) Q 1/13 + 3 / 13,23 + 3 / 23,33 + ... + 3 / 2013,2023
d) R 1 / 2.017,2016-1 / 2.016,2015-1 / 2015,2014 - ... -. 1 / (x + 1999) (x + 2000)
b2 : tìm x, biết :
a) 1 / (x + 1). (x + 2) + 1 / (x + 2). (x + 3) + 1 / (x + 3). (x + 4) + ... + 1 / (x + 1999). (x + 2000) 1 / x + 200 1/5
b) 2 / (x + 1). (x + 3) + 3 / (x + 3). (x + 6) + 4 / (x +...
Đọc tiếp
b1 :tính
a) N = (1/2 - 1). (1/3 - 1). (1/4 - 1) .... (1/2016 - 1). (1/2017 - 1)
b) P = (-1/1/2). (-1/1/3). (-1/1/4) ... (-1/1/2015). (2016/01/01)
c) Q = 1/13 + 3 / 13,23 + 3 / 23,33 + ... + 3 / 2013,2023
d) R = 1 / 2.017,2016-1 / 2.016,2015-1 / 2015,2014 - ... -. 1 / (x + 1999) (x + 2000)
b2 : tìm x, biết :
a) 1 / (x + 1). (x + 2) + 1 / (x + 2). (x + 3) + 1 / (x + 3). (x + 4) + ... + 1 / (x + 1999). (x + 2000) = 1 / x + 200 = 1/5
b) 2 / (x + 1). (x + 3) + 3 / (x + 3). (x + 6) + 4 / (x + 6). (x + 10) + ... + 10 / (x + 45). (x + 55) + 1 / x + 55 = 1/6
( chú ý : / là phần nha )
so sánh A= 1/1 x 2 x 3 + 1/2 x 3 x 4 + 1/3 x 4 x 5 + ...+ 1/ 2014 x 2015 x 2016 với 1/4
2A=2/1.2.3 + 2/2.3.4 + 2/3.4.5 + ...+2/2014.2015.2016
Ta có: 2/1.2.3=1/1.2-1/2.3; 2/2.3.4=1/2.3-1/3.4; 2/3.4.5=1/3.4-1/4.5; ....; 2/2014.2015.2016=1/2014.2015-1/2015.2016
=> 2A=1/1.2-1/2015.2016
=> 2A < 1/2 => A < 1/4
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Bài 1:tính
a) 1+(-2)+3+(-4)+5+(-6)+....+2015+(-2016)
b) 1+2-3+4+-6+....+2015
Bài 2:tìm x \(\in\) Z, biết:
a) 3.x+2=4
b) 3(x-1)-5=-20
c) (x-1).(x+2)=0
d) (x+1).(2x-5)=0
Giải cho mình với mai mình phải nộp rồi
B2:
a)3x+2=4
3x=4-2
3x=2
x=2/3
b)3(x-1)-5=-20
3(x-1)=-20+5
x-1=-15/3
x-1=-5
x=-5+1
x=-4
c)(x-1)(x+2)=0
nên x-1=0 hoặc x+2=0
x=0+1 x=0-2
x=1 x=-2
d)(x+1)(2x-5)=0
nên x+1=0 hoặc 2x-5=0
x=0-1 2x=0+5
x=1 x=5/2
còn b1 thì cậu đăng câu khác đi, t lười làm
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bài 1: a) 1+(-2)+3+(-4)+5+(-6)+....+2015+(-2016)
=[1+(-2)]+[3+(-4)]+[5+(-6)]+....+[2015+(-2016)]
=(-1)+(-1)+(-1)+...+(-1) (có 1008 số -1)
=(-1).1008
=-1008
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Giải phương trình:1,left(x^2-x+1right)^4+5x^46left(x^2-x+1right)^42,frac{x+4}{x-1}+frac{x-4}{x+1}frac{x-8}{x+2}+frac{x+8}{x-2}+frac{8}{3}3,left|x-2015right|^{2015}+left|x-2016right|^{2016}14,frac{5}{2x-3}-frac{1}{x+2}frac{5}{x-6}-frac{7}{2x-1}5,left(x+2008right)^4+left(x+2009right)^4frac{1}{8}
Đọc tiếp
Giải phương trình:
1,\(\left(x^2-x+1\right)^4+5x^4=6\left(x^2-x+1\right)^4\)
2,\(\frac{x+4}{x-1}+\frac{x-4}{x+1}=\frac{x-8}{x+2}+\frac{x+8}{x-2}+\frac{8}{3}\)
3,\(\left|x-2015\right|^{2015}+\left|x-2016\right|^{2016}=1\)
4,\(\frac{5}{2x-3}-\frac{1}{x+2}=\frac{5}{x-6}-\frac{7}{2x-1}\)
5,\(\left(x+2008\right)^4+\left(x+2009\right)^4=\frac{1}{8}\)
tớ ko bt lm abc , tớ lm d thôi nha , thứ lỗi
\(\frac{5}{2x-3}-\frac{1}{x+2}=\frac{5}{x-6}-\frac{7}{2x-1}\)
\(\frac{3x+13}{2x^2+x-6}=\frac{5}{x-6}+\frac{7}{1-2x}\)
\(\frac{3x+13}{\left(x+2\right)\left(2x-3\right)}=\frac{3x+37}{\left(x-6\right)\left(2x-1\right)}\)
\(\frac{10-9x}{-4x^3+32x^2-51x+18}=0\)
\(\Rightarrow\orbr{\begin{cases}x=-3\\x=\frac{10}{9}\end{cases}}\)