mARN: UGU - XXG - AAA - AUG

tARN: AXA - GGX - UUU - UAX

polypeptit: Xistein - prolin - lizin - metionin

a)

`4*(2y+3x)-3(x-3y)`

`=8y+12x-3x+9y`

`=8y+9y+12x-3x`

`=17y+9x`

b)

`x^2 +2x-x(7x-3)`

`=x^2 +2x-7x^2 +3x`

`=x^2 -7x^2 +2x+6x`

`= -6x^2 +8x`

Ta có: A = (x + 2)(x - 3) + x(x - 1) - 4 = x² - 3x + 2x - 6 + x² - x - 4 = 2x² - 2x - 10 = 2(x² - x + 1/4) - 21/2 = 2(x - 1/2)² - 21/2

Ta luôn có: 2(x - 1/2)² \(\ge\)0 \(\forall\)x

=> 2(x - 1/2)² - 21/2 \(\ge\)-21/2 \(\forall\)x

hay A \(\ge\)-21/2 \(\forall\)x

Dấu "=" xảy ra <=> x -1/2 = 0 <=> x = 1/2

vậy Min của A = -21/2 tại x = 1/2

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

\(\Leftrightarrow A=x^2-x-6+x^2-x-4\)

\(\Leftrightarrow A=2x^2-2x-10\)

\(\Leftrightarrow A=2\left(x^2-x-5\right)\)

\(\Leftrightarrow A=2\left(x^2-2.\frac{1}{2}x+\frac{1}{4}-\frac{21}{4}\right)\)

\(\Leftrightarrow A=2\left[\left(x-\frac{1}{2}\right)^2-\frac{21}{4}\right]\)

\(\Leftrightarrow A=2\left[\left(x-\frac{1}{2}\right)^2\right]-\frac{42}{4}\ge-\frac{42}{4}\)

Vậy \(A_{min}=\frac{-42}{4}\Leftrightarrow x=\frac{1}{2}\)

a: \(\dfrac{7x^3y^4}{35xy}=\dfrac{7xy\cdot x^2y^3}{7xy\cdot5}=\dfrac{x^2y^3}{5}\)

b: \(\dfrac{x^3-4x}{10-5x}=\dfrac{x\left(x-2\right)\left(x+2\right)}{-5\left(x-2\right)}=\dfrac{-x\left(x+2\right)}{5}=\dfrac{-x^2-2x}{5}\)

c: \(\dfrac{\left(x+2\right)\left(x+1\right)}{x^2-1}=\dfrac{\left(x+2\right)\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{x+2}{x-1}\)

d: \(\left(x^2-3x+2\right)\left(x+1\right)\)

\(=\left(x-2\right)\left(x-1\right)\left(x+1\right)\)

=(x-2)(x^2-1)

=>\(\dfrac{x^2-x-2}{x+1}=\dfrac{x^2-3x+2}{x-1}\)

e: \(\dfrac{x^3+8}{x^2-2x+4}=\dfrac{\left(x+2\right)\left(x^2-2x+4\right)}{x^2-2x+4}=x+2\)

3 * ( x - 9) + 15 = 12  + 243 : 9

3 * ( x - 9 ) + 15 = 39  

3 * ( x- 9 )         = 39 - 15 

3 * ( x - 9 )        = 24

       x - 9         = 24 : 3

       x - 9         = 8

        x             = 8 + 9

        x             = 17

Vậy...

^^ Cbht!!!   

3*(x-9)+15=12+243:9

3*(x-9)+15=12+27

3*(x-9)+15=39

3*(x-9)=39-15

3*(x-9)=24

x-9=24:3

x-9=8

x = 17

502-(x+5):2=318

(x+5):2=502-318

502-(x+5)=636

(x+5):2=184

(x+5)=184*2

(x+5)=368

x=363

120+[(999-9x):60]:24

3 * ( x - 9 ) + 15 = 12 + 243 : 9

3 * ( x - 9 ) + 15 = 12 + 27 = 39

        3 * ( x - 9 ) = 39 - 15 = 24

               x - 9    = 24 : 3 = 8

                       x  = 8 + 9

                       x  = 17 .

502 - ( x + 5 ) : 2 = 318

          ( x + 5 ) : 2 = 502 - 318 = 184

               x + 5      = 184 x 2 = 368

                          x = 368 - 5 

                           x = 363 .

120 + [ ( 999 - 9x ) : 60 ] : 24 = ?

\(\dfrac{1}{5}:x=\dfrac{7}{35}+\dfrac{5}{35}\)

\(\dfrac{1}{5}:x=\dfrac{12}{35}\)

\(x=\dfrac{1}{5}:\dfrac{12}{35}\)

\(x=\dfrac{1}{5}\times\dfrac{35}{12}\)

\(x=\dfrac{7}{12}\)

1/5 : x = 1/5 + 1/7

1/5 : x = 12/35

x = 1/5 : 12/35

x = 7/12

\(\dfrac{1}{5}:x=\dfrac{12}{35}\)

\(x=\dfrac{1}{5}:\dfrac{12}{35}\)

\(x=\dfrac{7}{12}\)

Ta có

a/3x^2y/3xy =3xy.x/3xy=x/2y^2

b/Ta có

x^2+2x/3x+6=x(x+2)/3(x+2)=x/3

c/Ta có

3x+3/3x = 3(x+1)/3x=x+1/x

-Vân đúng

a)

\(\dfrac{6}{13}\cdot\dfrac{8}{7}\cdot\dfrac{-26}{3}\cdot\dfrac{-7}{8}\)

\(=\dfrac{6}{13}\cdot\dfrac{-26}{3}\cdot\dfrac{8}{7}\cdot\dfrac{-7}{8}\)

\(=-4\cdot\left(-1\right)\\ =4\)

b)

\(\dfrac{6}{11}+\dfrac{11}{3}\cdot\dfrac{3}{22}\)

\(=\dfrac{6}{11}+\dfrac{1}{2}\\ =\dfrac{12}{22}+\dfrac{11}{22}\\ =\dfrac{23}{22}\)

a)=  (6/13*-26/3)* (8/7*-7/8)

= -4*-1=4

b=6/11+1/2=(12+11)/22=23/22

a. \(\dfrac{6.8.\left(-26\right).\left(-7\right)}{13.7.3.8}=\dfrac{2.3.8.\left(-13\right).2.\left(-7\right)}{13.7.3.8}=\dfrac{4}{1}=4\)

\(b.\dfrac{6}{11}+\dfrac{11.3}{3.11.2}\)

\(=\dfrac{6}{11}+\dfrac{1}{2}=\dfrac{23}{22}\)