\(P=-\left(2x+1\right)^2-7\left(y-3,5\right)^2+\dfrac{2}{3}\)

 vì \(\left\{{}\begin{matrix}-\left(2x+1\right)^2\le0,\forall x\\-7\left(y-3,5\right)^2\le0,\forall y\end{matrix}\right.\)

\(\Rightarrow P=-\left(2x+1\right)^2-7\left(y-3,5\right)^2+\dfrac{2}{3}\le\dfrac{2}{3}\)

Dấu "=" xảy ra khi

\(\left\{{}\begin{matrix}2x+1=0\\y-3,5=0\end{matrix}\right.\)

\(\Leftrightarrow\left\{{}\begin{matrix}x=-\dfrac{1}{2}\\y=3,5=\dfrac{7}{2}\end{matrix}\right.\)

Vậy \(GTLN\left(P\right)=\dfrac{2}{3}\left(tạix=-\dfrac{1}{2};y=\dfrac{7}{2}\right)\)

???????

a) | 5/4x -7/2| - | 5/8x + 3/5| = 0

|5/4x - 7/2| = | 5/8x + 3/5|

TH1: 5/4x - 7/2 = 5/8x + 3/5

=> 5/4x - 5/8x = 3/5 +7/2

5/8x = 41/10

x = 41/10:5/8

x = 164/25

TH2: 5/4x - 7/2 = -5/8x - 3/5

=> 5/4x + 5/8x  = -3/5 +7/2

15/8x  = 29/10

x = 29/10 : 15/8

x = 116/75

KL: x = 164/25 hoặc x = 116/75

các bài cn lại b lm tương tự nha! h lm dài lắm!

a: =>|5/4x-7/2|=|5/8x+3/5|

=>5/4x-7/2=5/8x+3/5 hoặc 5/4x-7/2=-5/8x-3/5

=>5/8x=41/10 hoặc 15/8x=29/10

=>x=164/25 hoặc x=116/75

b: =>3:|x/4-2/3|=6-21/5=9/5

=>|1/4x-2/3|=5/3

=>1/4x-2/3=5/3 hoặc 1/4x-2/3=-5/3

=>1/4x=7/3 hoặc 1/4x=-1

=>x=28/3 hoặc x=-4

c: \(\Leftrightarrow\left\{{}\begin{matrix}x>=0\\\left(2x-x-9\right)\left(2x+x+9\right)=0\end{matrix}\right.\Leftrightarrow x=9\)

e: =>|2x-7|=2x-7

=>2x-7>=0

=>x>=7/2

a) \(\left(\frac{7}{8}-\frac{3}{4}\right)\cdot\frac{1}{3}-\frac{2}{7}\cdot\left(3,5\right)=\left(\frac{7}{8}-\frac{3}{4}\right)\cdot\frac{1}{3}-\frac{2}{7}\cdot\frac{7}{2}\)

\(=\left(\frac{7}{8}-\frac{6}{8}\right)\cdot\frac{1}{3}-1=\frac{1}{8}\cdot\frac{1}{3}-1=\frac{1}{24}-\frac{24}{24}=-\frac{23}{24}\)

b) \(\left(\frac{3}{5}+0,415-\frac{3}{200}\right)\cdot2\frac{2}{3}\cdot0,25\)

\(=\left(\frac{3}{5}+\frac{83}{200}-\frac{3}{200}\right)\cdot\frac{8}{3}\cdot\frac{1}{4}\)

\(=\left(\frac{3}{5}+\frac{80}{200}\right)\cdot\frac{8}{3}\cdot\frac{1}{4}=\left(\frac{3}{5}+\frac{2}{5}\right)\cdot\frac{8}{3}\cdot\frac{1}{4}=1\cdot\frac{8}{3}\cdot\frac{1}{4}=1\cdot\frac{2}{3}\cdot\frac{1}{1}=\frac{2}{3}\)

c) \(\frac{5}{16}:0,125-\left(2\frac{1}{4}-0,6\right)\cdot\frac{10}{11}\)

\(=\frac{5}{16}:\frac{1}{8}-\left(\frac{9}{4}-\frac{3}{5}\right)\cdot\frac{10}{11}\)

\(=\frac{5}{16}\cdot8-\frac{33}{20}\cdot\frac{10}{11}=\frac{5}{2}-\frac{3}{2}=1\)

d) \(0,25:\left(10,3-9,8\right)-\frac{3}{4}=\frac{1}{4}:\left(\frac{103}{10}-\frac{98}{10}\right)-\frac{3}{4}\)

\(=\frac{1}{4}:\frac{1}{2}-\frac{3}{4}=\frac{1}{4}\cdot2-\frac{3}{4}=\frac{2}{4}-\frac{3}{4}=-\frac{1}{4}\)

Câu cuối tương tự

\(\left(\frac{2}{5}\right)^6:\left(\frac{2}{5}\right)^4=\left(\frac{2}{5}\right)^2=\frac{4}{25}\)

\(\left(\frac{3}{16}\right)^2:\left(\frac{9}{8}\right)^2=\frac{1}{12}\)

\(\left(\frac{2}{7}-\frac{1}{2}\right)^2=\frac{9}{196}\)

16-2x=40-3x

40-16=3x-2x

24=x

x=24

2x-16=40+x

  2x-x=40+16

      x=56

tick nhé cảm ơn

(x-7)(x+2005) = 0

\(\Rightarrow\) x-7 = 0

Vậy x = 7

2x-16=40+x=>x=56

16-2x=40-3x=>x=24

2(4x-2x)-7x=16=>x=-5,(3)

-2(-3-4x)-3(3x+7)=31=>x=-46

9(x+4)-4(2x+15)=3=>x=27

-2[x+(-7)]+(x-3)=12=>x=-1

(x-7)(x+2005)=0 =>x=7;-2005

a, \(\left(x-2\right)^3=-27\)

\(\Rightarrow\left(x-2\right)^3=-3^3\)

\(\Rightarrow x-2=-3\)

\(\Rightarrow x=-3+2=-1\)

b, \(\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)

\(\Rightarrow\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}=\dfrac{14}{7}=2\)

\(\Rightarrow\left[{}\begin{matrix}3,5-x=2\\3,5-x=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,5\\x=5,5\end{matrix}\right.\)

\(\left(x-2\right)^3=-27\)
\(\left(x-2\right)^3=-3^3\)
=> \(x-2=-3\)
\(x=-3+\left(-2\right)\)
\(x=-5\)
Vậy x=5

\(\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)
\(\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}\)
\(\left|3,5-x\right|=\dfrac{14}{7}\)
\(\left|3,5-x\right|=2\)
=> \(3,5-x=2hoặc3,5-x=-2\)
\(x=3,5-2\) hoặc \(x=3,5-\left(-2\right)\)
\(x=1,5\) hoặc \(x=3,5+2\)
\(x=1,5\) hoặc \(x=5,5\)
Vậy x=1,5 hoặc x=5,5

\(a)\left(x-2\right)^3=-27\)

\(\Rightarrow\left(x-2\right)^3=-3^3\)

\(\Rightarrow x-2=-3\)

\(\Rightarrow x=-3+2=-1\)

\(b)\left|3,5-x\right|+\dfrac{2}{7}=\dfrac{16}{7}\)

\(\Rightarrow\left|3,5-x\right|=\dfrac{16}{7}-\dfrac{2}{7}\)

\(\Rightarrow\left|3,5-x\right|=2\)

\(\Rightarrow\left[{}\begin{matrix}3,5-x=2\\3,5-x=-2\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1,5\\x=5,5\end{matrix}\right.\)

Chúc bạn học tốt!

5/2+x=-3/5

x=-3/5-5/2

x=-31/10

vậy x=-31/10

-2x+5=23

-2x=23-5

-2x=18

x=18:-2

x=-9

vậy x=-9

                                      Bài làm :

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

\(\Leftrightarrow x=-3,5-\frac{5}{2}=-6\)

\(-2x+5=23\)

\(\Leftrightarrow-2x=18\)

\(\Leftrightarrow x=-9\)

\(\frac{x}{21}=\frac{2}{7}-\frac{4}{3}\)

\(\Leftrightarrow\frac{x}{21}=-\frac{22}{21}\)

\(\Leftrightarrow x=-22\)

\(\frac{5}{3}x-\frac{2}{5}x=\frac{19}{10}\)

\(\Leftrightarrow x\left(\frac{5}{3}-\frac{2}{5}\right)=\frac{19}{10}\)

\(\Leftrightarrow\frac{19}{15}x=\frac{19}{10}\)

\(\Leftrightarrow x=\frac{3}{2}\)

Chúc bạn học tốt !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

x/21=2/7-4/3

x/21=-22/21

x×21=21×-22

x×21=-462

x=-462:21

x=22

vậy x=22