a. \(3-4x\left(25-2x\right)-8x^2+x-300=0\)

\(\Leftrightarrow3-100x+8x^2-8x^2+x-300=0\)

\(\Leftrightarrow-297-99x=0\)

\(\Leftrightarrow x=3\)

Vậy \(n_0\) của PT là: x=3

b. \(\Leftrightarrow\frac{\left(2-6x\right)}{5}-2+\frac{3x}{10}=7-\frac{3x+3}{4}\)

\(\Leftrightarrow\frac{\left(4-12x\right)}{5}-\frac{20}{10}+\frac{3x}{10}=\frac{\left(28-3x-3\right)}{4}\)

\(\Leftrightarrow\frac{\left(-16-9x\right)}{10}=\frac{\left(25-3x\right)}{4}\)

\(\Leftrightarrow-64-36x=250-30x\)

\(\Leftrightarrow-6x=314\)

\(\Leftrightarrow x=-\frac{157}{3}\)

Vậy -\(n_0\) của PT là: \(x=\frac{-157}{3}\)

c. \(5x+\frac{2}{6}-8x-\frac{1}{3}=4x+\frac{2}{5}-5\)

\(\Leftrightarrow-3x=4x-\frac{23}{5}\)

\(\Leftrightarrow7x=\frac{23}{5}\)

\(\Leftrightarrow x=\frac{23}{35}\)

Vậy \(n_0\) của PT là: \(x=\frac{23}{35}\)

d. \(3x+\frac{2}{3}-3x+\frac{1}{6}=2x+\frac{5}{3}\)

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

\(\Leftrightarrow x=-\frac{5}{12}\)

Vậy \(n_0\) của Pt là: \(x=-\frac{5}{12}\)

\(\left(2x-\dfrac{3}{4}\right)^2=\left(3-x\right)^2\)

\(\Rightarrow2x-\dfrac{3}{4}=3-x\)

\(3x=3\dfrac{3}{4}\)

\(x=\dfrac{5}{4}\)

\(a̸\)   

\(\frac{3}{5}-\frac{1}{2}.x=\frac{1}{4}\)

            \(\frac{1}{2}.x=\frac{3}{5}-\frac{1}{4}\)

           \(\frac{1}{2}.x=\frac{7}{20}\)

            \(\Rightarrow\frac{7}{10}\)

\(b̸\)

\(11,3+2\left[x-\frac{1}{3}\right]=\frac{25}{6}\)

\(2\left[x-\frac{1}{3}\right]=\frac{25}{6}-11,3\)

\(2\left[x-\frac{1}{3}\right]=\frac{-107}{15}\)

\(x-\frac{1}{3}=\frac{-107}{15}:2\)

 \(x-\frac{1}{3}=\frac{-107}{30}\)

\(x=\frac{-107}{30}+\frac{1}{3}\)

\(x=\frac{-97}{30}\)

\(a)\frac{3}{5}-\frac{1}{2}x=\frac{1}{4}\)

\(\implies\frac{1}{2}x=\frac{3}{5}-\frac{1}{4}\)

\(\implies\frac{1}{2}x=\frac{7}{20}\)

\(\implies x=\frac{7}{20}:\frac{1}{2}\)

\(\implies x=\frac{7}{10}\)

Vậy...

\(b) 11,3+2(x-\frac{1}{3})=\frac{25}{6}\)

\(\implies \frac{113}{10}+2x-2.\frac{1}{3}=\frac{25}{6}\)

\(\implies \frac{113}{10}+2x-\frac{2}{3}=\frac{25}{6}\)

\(\implies \frac{113}{10}+2x=\frac{25}{6}+\frac{2}{3}\)

\(\implies \frac{113}{10}+2x=\frac{29}{6}\)

\(\implies 2x=\frac{29}{6}-\frac{113}{10}\)

\(\implies 2x=\frac{-97}{15}\)

\(\implies x=\frac{-97}{30}\)

Vậy..

\(c)5x-435+2x+140+3x=565\)

\(\implies (5x+2x+3x)+(-435+140)=565\)

\(\implies 10x+(-295)=565\)

\(\implies 10x=565-(-295)\)

\(\implies 10x=860\)

\(\implies x=86\)

Vậy...

~ hok tốt a~

Tìm x:

1. 3x (2x + 3) - (2x + 5).(3x - 2) = 8

\(\Leftrightarrow6x^2+9x-6x^2+4x-15x+10=0 \)

\(\Leftrightarrow-2x+10=0\Leftrightarrow x=5\)

Vậy x = 5

2. 4x (x -1) - 3(x² - 5) -x² = (x - 3) - (x + 4)

\(\Leftrightarrow4x^2-4x-3x^2+15-x^2=x-3-x-4\)

\(\Leftrightarrow-4x+15=-7\)

\(\Leftrightarrow-4x=-22\Leftrightarrow x=\frac{11}{2}\)

Vậy x = \(\frac{11}{2}\)

3. 2 (3x -1) (2x +5) - 6 (2x - 1) (x + 2) = -6

\(\Leftrightarrow2\left(6x^2+15x-2x-5\right)-6\left(2x^2+4x-x-2\right)=-6\)

\(\Leftrightarrow12x^2+30x-4x-10-12x^2-24x+6x+12=-6\)

\(\Leftrightarrow8x=-8\Leftrightarrow x=-1\)

Vậy x = -1

4. 3 ( 2x - 1) (3x - 1) - (2x - 3) (9x - 1) - 3 = -3

\(\Leftrightarrow3\left(6x^2-2x-3x+1\right)-18x^2+2x+27x-3-3=-3\)

\(\Leftrightarrow18x^2-6x-9x+3-18x^2+2x+27x-6=-3\)

\(\Leftrightarrow14x=0\Leftrightarrow x=0\)

Vậy x = 0

5. (3x - 1) (2x + 7) - ( x + 1) (6x - 5) = (x + 2) - (x - 5)

\(\Leftrightarrow6x^2+21x-2x-7-6x^2+5x-6x+5=7\)

\(\Leftrightarrow18x=9\Leftrightarrow x=\frac{1}{2}\)

Vậy x = \(\frac{1}{2}\)

6. 3xy (x + y) - (x + y) (x² + y² + 2xy) + y³ = 27

\(\Leftrightarrow3x^2y+3xy^2-\left(x+y\right)^3+y^3=27\)

\(\Leftrightarrow3x^2y+3xy^2-x^3-y^3-3x^2y-3xy^2+y^3=27\)

\(\Leftrightarrow-x^3=27\)

\(\Leftrightarrow x=-3\)

Vậy x = -3

7. 3x (8x - 4) - 6x (4x - 3) = 30

\(\Leftrightarrow24x^2-12x-24x^2+12x=30\)

\(\Leftrightarrow0=30\) ( vô lý)

Vậy pt vô nghiệm

8. 3x (5 - 2x) + 2x (3x - 5) = 20

\(\Leftrightarrow15x-6x^2+6x^2-10x=20\)

\(\Leftrightarrow5x=20\Leftrightarrow x=4\)

Vậy x = 4

im chưa học\

Ta có : x² + 3x 

= x² + \(2.x.\frac{3}{2}+\left(\frac{3}{2}\right)^2-\left(\frac{3}{2}\right)^2\)

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

Ta có : (2x - 3)(4x² - 6x + 9) 

= (2x -3)(2x + 3)²

= (4x² - 9)(2x + 3)