2016 x 0,24 + 3/4 x 2016 + 2016 : 100
nhanh giúp mình
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1.
a) \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{99}\)
\(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x-1}=\frac{98}{99}\)
\(1-\frac{1}{x-1}=\frac{98}{99}\)
\(\frac{1}{x-1}=1-\frac{98}{99}\)
\(\frac{1}{x-1}=\frac{1}{99}\)
\(\Rightarrow x-1=99\)
\(\Rightarrow x=99+1=100\)
b) \(x-\frac{20}{11.13}-\frac{20}{13.15}-\frac{20}{15.17}-...-\frac{20}{53.55}=\frac{3}{11}\)
\(x-\left(\frac{20}{11.13}+\frac{20}{13.15}+\frac{20}{15.17}+...+\frac{20}{53.55}\right)=\frac{3}{11}\)
\(x-\left[10.\left(\frac{1}{11}-\frac{1}{13}\right)+10.\left(\frac{1}{13}-\frac{1}{15}\right)+10.\left(\frac{1}{15}-\frac{1}{17}\right)+...+10.\left(\frac{1}{53}-\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(x-\left[10.\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+...+\frac{1}{53}-\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(x-\left[10.\left(\frac{1}{11}-\frac{1}{55}\right)\right]=\frac{3}{11}\)
\(x-10.\frac{4}{55}=\frac{3}{11}\)
\(x-\frac{8}{11}=\frac{3}{11}\)
\(\Rightarrow x=\frac{3}{11}+\frac{8}{11}=1\)
c) 5x + 2 . 5x + 23 = 83
5x . ( 1 + 2 ) + 8 = 83
5x . 3 = 83 - 8
5x . 3 = 75
5x = 75 : 3
5x = 25
\(\Rightarrow\)5x = 52
\(\Rightarrow\)x = 2
2.
Ta thấy \(2016^{2016}>2016^{2016}-3\)
\(\Rightarrow B=\frac{2016^{2016}}{2016^{2016}-3}>\frac{2016^{2016}+2}{2016^{2016}-3+2}=\frac{2016^{2016}+2}{2016^{2016}-1}=A\)
\(\Rightarrow A< B\)
a) \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{99}\)
Ta có \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}=\frac{98}{99}\)
= \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}=\frac{98}{99}\)(áp dụng công thức)
= \(1-\frac{1}{x+1}=\frac{98}{99}\)
= \(\frac{1}{x+1}=1-\frac{98}{99}\)(quy tắc tìm số trừ)
= \(\frac{1}{x+1}=\frac{1}{99}\Rightarrow\frac{1}{x+1}=\frac{1}{98+1}\Rightarrow x=98\)
Vậy x = 98 :)
Còn nữa, công thức mà mình áp dụng là: \(\frac{a}{b.c}=\frac{1}{b}-\frac{1}{c}\)nếu \(a=c-b\)
chấm hỏi lớn ???????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????
\(\frac{2016-x}{2017}\)+\(\frac{2017-x}{2016}\)+2=\(\frac{2016}{2017-x}\)+\(\frac{2017}{2016-x}\)+2
\(\frac{4033-x}{2017}\)+\(\frac{4033-x}{2016}\)=\(\frac{4033-x}{2017-x}\)+\(\frac{4033-x}{2016-x}\)
(4033-x)(\(\frac{1}{2017}\)+\(\frac{1}{2016}\)-\(\frac{1}{2017-x}\)-\(\frac{1}{2016-x}\))=0
=>\(\hept{\begin{cases}4033-x=0\\\frac{1}{2017}+\frac{1}{2016}-\frac{1}{2017-x}-\frac{1}{2016-x}\end{cases}}=0\)
=>x=4033
x=0
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mk ko biết xin lỗi bạn nha!!!
mk ko biết xin lỗi bạn nha!!!
mk ko biết xin lỗi bạn nha!!!
ta có ; x-3/2015 -1 +x-2/2016 -1 = x-2016/2 -1 +x-2015/3-1
x-2018/2015 + x-2018/2016 = x-2018/2 +x-2018/3
(x-2018)*(1/2015+1/2016-1/2-1/3)=0
vi (1/2015+1/2016-1/2-1/3) luon khac 0
suy ra : x-2018 = 0 suy ra x=2018
\(\frac{x-3}{2015}+\frac{x-2}{2016}=\frac{x-2016}{2}+\frac{x-2015}{3}\)
trừ 2 vế với 2, ta có:
\(\frac{x-3}{2015}+\frac{x-2}{2016}-2=\frac{x-2016}{2}+\frac{x-2015}{3}-2\)
\(\left(\frac{x-3}{2015}-1\right)+\left(\frac{x-2}{2016}-1\right)=\left(\frac{x-2016}{2}-1\right)+\left(\frac{x-2015}{3}-1\right)\)
\(\frac{x-2018}{2015}+\frac{x-2018}{2016}=\frac{x-2018}{2}+\frac{x-2018}{3}\)
\(\left(x-2018\right)\frac{1}{2015}+\left(x-2018\right)\frac{1}{2016}=\left(x-2018\right)\frac{1}{2}+\left(x-2018\right)\frac{1}{3}\)
\(\left(x-2018\right)\left(\frac{1}{2015}+\frac{1}{2016}\right)=\left(x-2018\right)\left(\frac{1}{2}+\frac{1}{3}\right)\)
\(\left(x-2018\right)\left(\frac{1}{2015}+\frac{1}{2016}\right)-\left(x-2018\right)\left(\frac{1}{2}+\frac{1}{3}\right)=0\)
\(\left(x-2018\right)\left(\frac{1}{2015}+\frac{1}{2016}-\frac{1}{2}-\frac{1}{3}\right)=0\)
Mà \(\frac{1}{2015}+\frac{1}{2016}-\frac{1}{2}-\frac{1}{3}\ne0\)
\(\Rightarrow x-2018=0\Leftrightarrow x=2018\)
Vậy tập nghiệm của PT là\(S=\left\{2018\right\}\)
9x(2016-x) =2016
2016-x =2016:9
2016-x =224
x =2016-224
x =1792
Vậy x=1792
đặt \(\sqrt{x^2+2016}=y\left(y\ge0\right)\) =>\(2016=y^2-x^2\)
khi đó pt trên trở thành
\(x^4+y=y^2-x^2\)
<=> \(\left(x^4-y^2\right)+\left(x^2+y\right)=0\)
<=>\(\left(x^2+y\right)\left(x^2-y\right)+\left(x^2+y\right)=0\)
<=>\(\left(x^2+y\right)\left(x^2-y+1\right)=0\)
<=>\(\orbr{\begin{cases}x^2+y=0\left(loai\right)\\x^2=y-1\end{cases}}\)
với x^2=y-1 thì ta có pt \(x^2=\sqrt{x^2+2016}-1\)
<=>\(\left(\sqrt{x^2+2016}+\frac{1}{2}\right)^2=\frac{8061}{4}\)
đến đây bạn tự giải nốt nha
Do |x+2015| lớn hoặc = 0 với mọi x nên A bé hơn hoặc bằng -2016
Dấu "=" xảy ra khi và chỉ khi x+2015=0
=> x=-2015
= 2016 x 0,24 + 0,75 x 2016 + 2016 x 0,01
= 2016 x ( 0,24 + 0,75 + 0,01 )
= 2016 x 1
= 2016
=2016 x 0,24 + 2016 x 0,75 + 2016 x 0,01
=2016 x ( 0,24 + 0,75 + 0,01 )
=2016 x 1
=2016