3/ 4x=1 <=>x=1/4

4/7x=9/8-0,125 <=>7x=1<=>x=1/7

3/4x=1

<=>x=4/3

4/7x=9/8-0,125

<=>4/7x=9/8-1/8=8/8=1

<=>x=7/4

\(\frac{3}{4}x=1\)

\(\Leftrightarrow x=\frac{4}{3}\)

\(\frac{4}{7}x=\frac{9}{8}-0,125\)

\(\Leftrightarrow\frac{4}{7}x=\frac{9}{8}-\frac{1}{8}\)

\(\Leftrightarrow\frac{4}{7}x=1\)

\(\Leftrightarrow x=\frac{7}{4}\)

Lời giải:
a)

\(\frac{3}{4}x=1\)

\(x=1:\frac{3}{4}=1.\frac{4}{3}=\frac{4}{3}\)

b)

\(\frac{4}{7}x=\frac{9}{8}-0,125\)

\(\frac{4}{7}x=1\)

\(x=1:\frac{4}{7}\)

\(x=\frac{7}{4}\)

a) 3/4x = 1

         x = 1 : 3/4

         x = 4/3

b) 4/7x = 9/8 - 0,125

    4/7x = 1

        x = 1 : 4/7

        x = 7/4

a)\(\frac{3}{4}\). x =1

             x=1:\(\frac{3}{4}\)

             x=      \(\frac{4}{3}\)

b)\(\frac{4}{7}\).x=\(\frac{9}{8}\)-0,125

\(\frac{4}{7}\).x=1,125-0,125

\(\frac{4}{7}\).x=1

         x=1:\(\frac{4}{7}\)

         x=\(\frac{7}{4}\)

CHÚC BẠN HỌC GIỎI

K MÌNH NHÉ

x = 7/4

Nho tk cho minh nhe

b)

ĐKXĐ: \(x\ne-\dfrac{3}{2}\)

Để phân số \(B=\dfrac{4x+1}{2x+3}\) là số nguyên thì \(4x+1⋮2x+3\)

\(\Leftrightarrow4x+6-5⋮2x+3\)

mà \(4x+6⋮2x+3\)

nên \(-5⋮2x+3\)

\(\Leftrightarrow2x+3\inƯ\left(-5\right)\)

\(\Leftrightarrow2x+3\in\left\{1;-1;5;-5\right\}\)

\(\Leftrightarrow2x\in\left\{-2;-4;2;-8\right\}\)

hay \(x\in\left\{-1;-2;1;-4\right\}\)(thỏa ĐK)

Vậy: \(x\in\left\{-1;-2;1;-4\right\}\)

A.

^{_{\(\Leftrightarrow\)}} 9x - 2x - 6 = 3x + 1

\(\Leftrightarrow\) 4x = 7

\(\Leftrightarrow\) x = \(\dfrac{7}{4}\)

B.

\(\Leftrightarrow\dfrac{5\left(x+3\right)}{\left(x-3\right)\left(x+3\right)}-\dfrac{4\left(x-3\right)}{\left(x+3\right)\left(x-3\right)}=\dfrac{x-13}{\left(x-3\right)\left(x+3\right)}\)

\(\Leftrightarrow\) 5x + 15 - 4x +12 = x - 13

\(\Leftrightarrow\) 0x = -40 ( phương trình vô nghiệm)

C.

\(\Leftrightarrow\) 7x + 8 \(\ge\) 3x -3

\(\Leftrightarrow\) 4x \(\ge\) - 11

\(\Leftrightarrow\)\(x\ge\dfrac{-11}{4}\)

Mik ko ghi đề

Câu a)x=41×13      x=533

Câu b)x=1428:14       x=102

Câu c)4x=0×17

            4x=0

            x=0+4

            x=4Mik mỏi tay ko viết nữa sorry

\(b,4x^2-x-5=0\)

\(\Leftrightarrow4x^2-5x+4x-5=0\)

\(\Leftrightarrow x\left(4x-5\right)+4x-5=0\)

\(\Leftrightarrow\left(4x-5\right)\left(x+1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=-1\\x=\frac{5}{4}\end{cases}}\)

Bài 2

\(a,x^3+5x^2+3x-9\)

\(\Leftrightarrow x^3-x^2+6x^2-6x+9x-9\)

\(\Leftrightarrow x^2\left(x-1\right)+6x\left(x-1\right)+9\left(x-1\right)\)

\(\Leftrightarrow\left(x-1\right)\left(x^2+6x+9\right)\)

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

b,\(x^3-7x-6\)

\(\Leftrightarrow x^3-3x^2+3x^2-9x+2x-6\)

\(\Leftrightarrow x^2\left(x-3\right)+3x\left(x-3\right)+2\left(x-3\right)\)

\(\Leftrightarrow\left(x-3\right)\left(x^2+3x+2\right)\)

\(\Leftrightarrow\left(x-3\right)\left(x+1\right)\left(x+2\right)\)

c,\(3x^3-7x^2+17x-5\)

\(\Leftrightarrow3x^3-x^2-6x^2+2x+15x-5\)

\(\Leftrightarrow x^2\left(3x-1\right)-2x\left(3x-1\right)+5\left(3x-1\right)\)

\(\Leftrightarrow\left(3x-1\right)\left(x^2-2x+5\right)\)

\(4x^2-x-5=0\)

<=>  \(4x^2+4x-5x-5=0\)

<=>   \(4x\left(x+1\right)-5\left(x+1\right)=0\)

<=>  \(\left(x+1\right)\left(4x-5\right)=0\)

tự lm tiếp

Bài 1:

a)\(28x^3+15x^2+75x+125=0\)

\(\Leftrightarrow\left(4x+5\right)\left(7x^2-5x+25\right)=0\)

Dễ thấy: \(7x^2-5x+25=7\left(x-\frac{5}{14}\right)^2+\frac{675}{28}>0\)

\(\Rightarrow4x+5=0\Rightarrow x=-\frac{5}{4}\)

b)\(4x^2-x-5=0\)

\(\Leftrightarrow\left(x+1\right)\left(4x-5\right)=0\)

\(\Rightarrow x=-1;x=\frac{5}{4}\)

Bài 2:

a)\(x^3+5x^2+3x-9\)

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

b)\(x^3-7x-6\)

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

c)\(3x^3-7x^2+17x-5\)

\(=\left(3x-1\right)\left(x^2-2x+5\right)\)

\(4x^2-x-5=0\)

<=> \(4x^2+4x-5x-5=0\)

<=>  \(4x\left(x+1\right)-5\left(x+1\right)=0\)

<=>  \(\left(x+1\right)\left(4x-5\right)=0\)

tự giải nốt

a)x:13=41

x=41.13

x=533

Vậy x=533

b)1428:x=14

x=1428:14

x=102

Vậy x=102

c)4x:17=0

4x=0.17

x=0:4

x=0

Vậy x=0

d)7x-8=713

7x=713+8

7x=721

x=721:7

x=103

Vậy x=103

e)8(x-3)=0

x-3=0:8

x-3=0

x=0+3

x=3

Vậy x=3