a) x = 15

b) x = 11

c) x = 68

d) x = 310

(x4)3=x6x19

a) x = 15.              b)      x = 11.        c) x = 68.              d) x = 310

Tìm xx biết:    \left(x^{4}\right)^{3}=\dfrac{x^{19}}{x^{6}}(x4)3=x6x19​

Trả lời: x=x= 

Ta tính nhẩm như sau:

3x4=12     2x5=10    5x3=15     4x2=8

12:3=4      10:2=5    15:3=5      8:2=4

12:4=3      10:5=2     15:5=3     8:4=2

3x4 = 12               2x5 = 10        5x3 = 15                  4x2 =8

12 : 3 = 4              10 : 2 = 5       15 : 3 = 5                8 : 2 = 4

12 : 4 =3               10 :5 = 2        15 : 5 = 3                8 : 4 = 2

((x - 2)(x + 10))/3 - ((x + 40)(x + 10))/12 = ((x - 2)(x + 4))/4

<=> 4(x - 2)(x + 10) - (x + 4)(x + 10) = 3(x - 2)(x + 4)

<=> 4x^2 + 40x - 8x - 80 - x^2 - 10x - 4x - 40 = 3x^2 + 12x - 6x - 24

<=> 3x^2 + 18x - 120 = 3x^2 + 6x - 24

<=> 18x - 120 = 6x - 24

<=> 18x - 120 - 6x = -24

<=> 12x - 120 = -24

<=> 12x = -24 + 120

<=> 12x = 96

<=> x = 8

Hướng dẫn giải:

a) 5 x (10 + 9)

Cách 1:

5 x (10 + 9) = 5 x 19 = 95

Cách 2:

5 x (10 + 9) = 5 x 10 + 5 x 9 = 50 + 45 = 95

b) 10 x (30 + 5)

Cách 1:

10 x (30 + 5) = 10 x 35 = 350

Cách 2:

10 x (30 + 5) = 10 x 30 + 10 x 5 = 300 + 50 = 350

Hướng dẫn giải nè :

a) 5 x (10 + 9)

Cách 1:

5 x (10 + 9) = 5 x 19 = 95

Cách 2:

5 x (10 + 9) = 5 x 10 + 5 x 9 = 50 + 45 = 95

b) 10 x (30 + 5)

Cách 1:

10 x (30 + 5) = 10 x 35 = 350

Cách 2:

10 x (30 + 5) = 10 x 30 + 10 x 5 = 300 + 50 = 350

a, x + 12 = 4 x 4

a, x + 12 =16

x = 16-12

x = 4

b, x + 10 = 20 x 3

b, x + 10 = 60

b, x = 60 - 10

x = 50

a) x=4

b)x=50

a, x + 12 = 4 x 4

    x + 12 = 16

            x = 16 - 12

             x = 4

b, x + 10 = 20 x 3

    x + 10 = 60

            x = 60 - 10

            x = 50

1) \(\frac{4}{5}.x=\frac{8}{35}\Rightarrow x=\frac{8}{25}:\frac{4}{5}\Rightarrow x=\frac{2}{5}\)

       \(\frac{2}{3}.x+\frac{1}{4}=\frac{7}{12}\Rightarrow\frac{2}{3}.x=\frac{7}{12}-\frac{1}{4}\)

                                          \(\Rightarrow\frac{2}{3}.x=\frac{1}{3}\)

                                         \(\Rightarrow x=\frac{1}{3}:\frac{2}{3}\)

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

\(\frac{x}{10}=\frac{3}{10}\Rightarrow x=\frac{10.3}{10}\Rightarrow x=3\)

a) Ta có: \(\frac{-6}{12}< \frac{x}{12}< \frac{-4}{12}\Rightarrow-6< x< -4\Rightarrow x=-5\)

b) \(\frac{-6}{5}+\frac{13}{15}< \frac{x}{15}< \frac{-2}{5}+\frac{1}{3}\)

\(\Rightarrow\frac{-1}{3}< \frac{x}{15}< \frac{-1}{15}\)

\(\Rightarrow\frac{-5}{15}< \frac{x}{15}< \frac{-1}{15}\)

\(\Rightarrow-5< x< -1\)

\(\Rightarrow x=\left\{-4;-3;-2\right\}\)

a) = 20/91

b) = 5/6 - 1/4 = 3/8

c) 2/9 + 1/10 = 29/90

A= 20/19

B=5/6-1/4=3/8

C= 2/9+ 1/10 = 29/90 nha bạn ?

\(\Leftrightarrow4\left(x-2\right)\left(x+10\right)-\left(x+4\right)\left(x+10\right)-3\left(x-2\right)\left(x+4\right)=0\)

\(\Leftrightarrow4\left(x^2+8x-20\right)-\left(x^2+14x+40\right)-3\left(x^2+2x-8\right)=0\)

\(\Leftrightarrow12x-96=0\Rightarrow x=8\)

=) vào ngay quả bảng phá dấu GTTĐ, cay thế :< 

a, \(3x+\frac{2x}{3}-3=\frac{5}{2}x-2\Leftrightarrow\frac{18x+4x-18}{6}=\frac{15x-12}{6}\)

\(\Rightarrow22x-18=15x-12\Leftrightarrow7x=6\Leftrightarrow x=\frac{6}{7}\)

Vậy pt có nghiệm x = 6/7 

b, \(\frac{3\left(2x+1\right)}{4}-\frac{5x+3}{6}+\frac{x+1}{3}=\frac{x+7}{12}\)

\(\Leftrightarrow\frac{9\left(2x+1\right)-2\left(5x+3\right)+4\left(x+1\right)}{12}=\frac{x+7}{12}\)

\(\Rightarrow18x+9-10x-6+4x+4=x+7\)

\(\Leftrightarrow12x+7=x+7\Leftrightarrow11x=0\Leftrightarrow x=0\)

Vậy pt có nghiệm là x = 0 

c, \(\frac{3x}{x-3}-\frac{x-3}{x+3}=2\)ĐK : \(x\ne\pm3\)

\(\Leftrightarrow\frac{3x\left(x+3\right)-\left(x-3\right)^2}{\left(x-3\right)\left(x+3\right)}=\frac{2\left(x-3\right)\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}\)

\(\Rightarrow3x^2+9x-x^2+6x-9=2\left(x^2-9\right)\)

\(\Leftrightarrow2x^2+15x-9=2x^2-18\Leftrightarrow15x+9=0\Leftrightarrow x=-\frac{9}{15}=-\frac{3}{5}\)

Vậy pt có nghiệm là x = -3/5 

d, Sửa đề :  \(\frac{x+10}{2003}+\frac{x+6}{2007}+\frac{x+2}{2011}+3=0\)

\(\Leftrightarrow\frac{x+10}{2003}+1+\frac{x+6}{2007}+1+\frac{x+2}{2011}+1=0\)

\(\Leftrightarrow\frac{x+2013}{2003}+\frac{x+2013}{2007}+\frac{x+2013}{2011}=0\)

\(\Leftrightarrow\left(x+2013\right)\left(\frac{1}{2003}+\frac{1}{2007}+\frac{1}{2011}\ne0\right)=0\Leftrightarrow x=-2013\)

Vậy pt có nghiệm là x = -2013 

e, \(4\left(x+5\right)-3\left|2x-1\right|=10\)

\(\Leftrightarrow4x+20-3\left|2x-1\right|=10\Leftrightarrow-3\left|2x-1\right|=-10-4x\)

\(\Leftrightarrow\left|2x-1\right|=\frac{10+4x}{3}\)

ĐK : \(\frac{10+4x}{3}\ge0\Leftrightarrow10+4x\ge0\Leftrightarrow x\ge-\frac{10}{4}=-\frac{5}{2}\)

TH1 : \(2x-1=\frac{10+4x}{3}\Rightarrow6x-3=10+4x\Leftrightarrow2x=13\Leftrightarrow x=\frac{13}{2}\)( tm )

TH2 : \(2x-1=\frac{-10-4x}{3}\Rightarrow6x-3=-10-4x\Leftrightarrow10x=-7\Leftrightarrow x=-\frac{7}{10}\)( tm )

f, để mình xem lại đã, quên cách phá GTTĐ rồi :v :>