\(2^{2^{11}}+3^{3^{11}}\) và \(2^{2^{12}}+3^{3...">
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28 tháng 10 2018

\(I=3\left(x^2-\dfrac{5}{3}x+1\right)\)

\(I=3\left(x^2-2.x.\dfrac{5}{6}+\left(\dfrac{5}{6}\right)^2-\left(\dfrac{5}{6}\right)^2+1\right)\)

\(I=3\left[\left(x-\dfrac{5}{6}\right)^2+\dfrac{11}{36}\right]\)

\(I=3\left(x-\dfrac{5}{6}\right)^2+\dfrac{11}{12}\)

28 tháng 10 2018

mình ra là \(\dfrac{11}{36}\)mà bn

bn coi lại đi

I=3x2-5x+3

I=3(x2-\(\dfrac{5}{3}\)x+1)

I=3[x2-2.x.\(\dfrac{5}{3}\)+\(\left(\dfrac{5}{6}\right)^2\)-\(\left(\dfrac{5}{6}\right)^2\)+1]

I=3(x-\(\dfrac{5}{3}\))2+\(\dfrac{11}{36}\)

I=3(x-\(\dfrac{5}{3}\))2+\(\dfrac{11}{36}\)\(\dfrac{11}{36}\)

vậy Min I= \(\dfrac{11}{36}\)khi x =\(\dfrac{5}{3}\)

Theo mik nghĩ là vậy á

CHÚC BN HỌC TỐT

19 tháng 6 2018

Giải:

1) \(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)

\(=\dfrac{-1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)

\(=\dfrac{-1}{12}-\dfrac{55}{24}\)

\(=\dfrac{-19}{8}\)

2) \(-1,75-\left(\dfrac{-1}{9}-2\dfrac{1}{18}\right)\)

\(=-\dfrac{7}{4}+\dfrac{1}{9}+2\dfrac{1}{18}\)

\(=-\dfrac{7}{4}+\dfrac{1}{9}+\dfrac{37}{18}\)

\(=\dfrac{5}{12}\)

3) \(-\dfrac{5}{6}-\left(-\dfrac{3}{8}+\dfrac{1}{10}\right)\)

\(=-\dfrac{5}{6}+\dfrac{3}{8}-\dfrac{1}{10}\)

\(=-\dfrac{67}{120}\)

4) \(\dfrac{2}{5}+\left(-\dfrac{4}{3}\right)+\left(-\dfrac{1}{2}\right)\)

\(=\dfrac{2}{5}-\dfrac{4}{3}-\dfrac{1}{2}\)

\(=-\dfrac{43}{30}\)

5) \(\dfrac{3}{12}-\left(\dfrac{6}{15}-\dfrac{3}{10}\right)\)

\(=\dfrac{3}{12}-\dfrac{6}{15}+\dfrac{3}{10}\)

\(=\dfrac{3}{20}\)

6) \(\left(8\dfrac{5}{11}+3\dfrac{5}{8}\right)-3\dfrac{5}{11}\)

\(=8\dfrac{5}{11}+3\dfrac{5}{8}-3\dfrac{5}{11}\)

\(=8+\dfrac{5}{11}+3+\dfrac{5}{8}-3-\dfrac{5}{11}\)

\(=8+\dfrac{5}{8}\)

\(=\dfrac{69}{8}\)

7) \(-\dfrac{1}{4}.13\dfrac{9}{11}-0,25.6\dfrac{2}{11}\)

\(=-\dfrac{1}{4}.13\dfrac{9}{11}-\dfrac{1}{4}.6\dfrac{2}{11}\)

\(=-\dfrac{1}{4}\left(13\dfrac{9}{11}+6\dfrac{2}{11}\right)\)

\(=-\dfrac{1}{4}\left(13+\dfrac{9}{11}+6+\dfrac{2}{11}\right)\)

\(=-\dfrac{1}{4}\left(13+6+1\right)\)

\(=-\dfrac{1}{4}.20=-5\)

8) \(\dfrac{4}{9}:\left(-\dfrac{1}{7}\right)+6\dfrac{5}{9}:\left(-\dfrac{1}{7}\right)\)

\(=\dfrac{4}{9}\left(-7\right)+6\dfrac{5}{9}\left(-7\right)\)

\(=-7\left(\dfrac{4}{9}+6\dfrac{5}{9}\right)\)

\(=-7\left(\dfrac{4}{9}+6+\dfrac{5}{9}\right)\)

\(=-7\left(6+1\right)\)

\(=-7.7=-49\)

Vậy ...

18 tháng 8 2021

Áp dụng bất đẳng thức AM-GM ta có :

\(B=\frac{12}{x-1}+\frac{x-1+1}{3}=\frac{12}{x-1}+\frac{x-1}{3}+\frac{1}{3}\ge2\sqrt{\frac{12}{x-1}\cdot\frac{x-1}{3}}+\frac{1}{3}=4+\frac{1}{3}=\frac{13}{3}\)

Dấu "=" xảy ra <=> \(\frac{12}{x-1}=\frac{x-1}{3}\Rightarrow x=7\left(x\ge1\right)\). Vậy MinB = 13/3

18 tháng 11 2016

Thay các giá trị Q(1) , Q(2) , Q(3) , Q(4) vào Q(x) được :

\(Q\left(1\right)=1+m+n+p+q=5\)

\(Q\left(2\right)=16+8m+4n+2p+q=7\)

\(Q\left(3\right)=81+27m+9n+3p+q=9\)

\(Q\left(4\right)=256+64m+16n+4p+q=11\)

Ta có hệ \(\begin{cases}m+n+p+q=4\\8m+4n+2p+q=-9\\27m+9n+3p+q=-72\\64m+16n+4p+q=-245\end{cases}\)

\(\Leftrightarrow\begin{cases}m=-10\\n=35\\p=-48\\q=27\end{cases}\)

Từ đó bạn thay vào tính Q(10) , Q(11) , Q(12) , Q(13) nhé ^^

 

18 tháng 11 2016

hell

29 tháng 3 2020

7) Ta có : \(\frac{5x-2}{3}=\frac{5-3x}{3}\)

=> \(5x-2=5-3x\)

=> \(5x+3x=5+2\)

=> \(8x=7\)

=> \(x=\frac{8}{7}\)

8) Ta có : \(\left(6x+3\right)\left(5x-20\right)=0\)

=> \(\left[{}\begin{matrix}6x+3=0\\5x-20=0\end{matrix}\right.\)

=> \(\left[{}\begin{matrix}x=-\frac{1}{2}\\x=4\end{matrix}\right.\)

10) ĐKXĐ : \(x\ne5\)

Ta có : \(\frac{2x-5}{x+5}=3\)

=> \(2x-5=3\left(x+5\right)\)

=> \(2x-5-3x-15=0\)

=> \(x=-20\) ( TM )

11) ĐKXĐ : \(x-2\ne0\)

=> \(x\ne2\)

Ta có : \(\frac{1}{x-2}+4=\frac{x-3}{2-x}\)

=> \(\frac{1}{x-2}+\frac{4\left(x-2\right)}{x-2}=\frac{3-x}{x-2}\)

=> \(1+4\left(x-2\right)=3-x\)

=> \(1+4x-8-3+x=0\)

=> \(5x=10\)

=> x = 2 ( KTM )

Vậy phương trình trên vô nghiệm.

29 tháng 3 2020

7) \(\frac{5x-2}{3}=\frac{5-3x}{3}\)

\(\Leftrightarrow\) 5x-2=5-3x

\(\Leftrightarrow\) 5x+3x=5+2

\(\Leftrightarrow\) 8x=7

\(\Leftrightarrow\) x=\(\frac{7}{8}\)

8) (6x+3)(5x-20)=0

\(\Rightarrow\) 6x+3=0 hoặc 5x-20=0

\(\Rightarrow\) 6x=-3

\(\Rightarrow\) x=\(\frac{-1}{2}\)