a) \(5x\left(3x-7\right)-15x\left(x-1\right)=3\)

\(\Rightarrow15x^2-35x-15x^2+15x=3\)

\(\Rightarrow-20x=3\)

\(\Rightarrow x=-\dfrac{3}{20}\)

b) \(\left(4x+2\right)\left(6x-3\right)-\left(8x+5\right)\left(3x-4\right)=2\)

\(\Rightarrow24x^2+12x-12x-6-24x^2-15x+24x+20=2\)

\(\Rightarrow9x+14=2\)

\(\Rightarrow9x=-12\)

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

c) \(7x^2-21x=0\)

\(\Rightarrow7x\left(x-3\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}7x=0\\x-3=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\)

d) \(9x^2-6x+1=0\)

\(\Rightarrow\left(3x\right)^2-2.3x+1=0\)

\(\Rightarrow\left(3x-1\right)^2=0\)

\(\Rightarrow3x-1=0\)

\(\Rightarrow3x=1\)

\(\Rightarrow x=\dfrac{1}{3}\)

e) \(16x^2-49=0\)

\(\Rightarrow\left(4x\right)^2-7^2=0\)

\(\Rightarrow\left(4x-7\right)\left(4x+7\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}4x-7=0\\4x+7=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}4x=7\\4x=-7\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{7}{4}\\x=-\dfrac{7}{4}\end{matrix}\right.\)

f) \(5x^3-20x=0\)

\(\Rightarrow5x\left(x^2-4\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}5x=0\\x^2-4=0\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x^2=4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=5\\x=2\\x=-2\end{matrix}\right.\)

Phân tích thành nhân tử r tìm x nhé bạn. k đi mình làm

a) \(3x^2-5x-12=0\)

\(\Leftrightarrow3x^2+4x-9x-12=0\)

\(\Leftrightarrow x\left(3x+4\right)-3\left(3x+4\right)=0\)

\(\Leftrightarrow\left(3x+4\right)\left(x-3\right)=0\)

\(\Rightarrow\orbr{\begin{cases}3x+4=0\\x-3=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=-\frac{4}{3}\\x=3\end{cases}}\)

b) \(7x^2-9x+2=0\)

\(\Leftrightarrow7x^2-7x-2x+2=0\)

\(\Leftrightarrow7x\left(x-1\right)-2\left(x-1\right)=0\).

\(\Leftrightarrow\left(7x-2\right)\left(x-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}7x-2=0\\x-1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{2}{7}\\x=1\end{cases}}\)

a)3x²+4x-9x-12=0

=>(3x²+4x)-(9x+12)=0

=> x(3x+4)-3(3x+4)=0

=> (x-3)(3x+4)=0  =>x-3=0 hoặc 3x+4=0

=>tự tính

b)7x²-9x+2=0

=>7x²-7x-2x+2=0

=>(7x²-7x)-(2x-2)=0

=>7x(x-1)-2(x-1)=0

=>(7x-2)(x-1)=0

=>như câu a

bạn chỉ biết làm 2 câu thôi

sai đề rồi bạn ơi

a) \(3x^3+6x^2-4x=0\) \(\Leftrightarrow\) \(x\left(3x^2+6x-4\right)=0\)

\(\Leftrightarrow\) \(\left\{{}\begin{matrix}x=0\\3x^2+6x-4=0\end{matrix}\right.\) \(\Leftrightarrow\) \(\left\{{}\begin{matrix}x=0\\\left\{{}\begin{matrix}x=\dfrac{-3+\sqrt{21}}{3}\\x=\dfrac{-3-\sqrt{21}}{3}\end{matrix}\right.\end{matrix}\right.\)

vậy phương trình có 2 nghiệm \(x=0;x=\dfrac{-3+\sqrt{21}}{3};x=\dfrac{-3-\sqrt{21}}{3}\)

\(\left(x^2-3x\right)^2-5\left(x^2-3x\right)+4=0\)

Đặt \(x^2-3x=a\) ta được:

\(a^2-5a+4=0\Rightarrow\left[{}\begin{matrix}a=1\\a=4\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x^2-3x=1\\x^2-3x=4\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x^2-3x-1=0\\x^2-3x-4=0\end{matrix}\right.\) \(\Rightarrow\left[{}\begin{matrix}x=\frac{3+\sqrt{13}}{2}\\x=\frac{3-\sqrt{13}}{2}\\x=-1\\x=4\end{matrix}\right.\)

a) (25x⁵ – 5x⁴ + 10x²) : 5x² = (25x⁵ : 5x² ) - (5x⁴ : 5x² ) + (10x² : 5x² )

= 5x³ – x² + 2

b) (15x³y² – 6x²y – 3x²y²) : 6x²y

= (15x³y² : 6x²y) + (– 6x²y : 6x²y) + (– 3x²y² : 6x²y)

= \(\dfrac{15}{6}\)xy - 1 - \(\dfrac{3}{6}\)y = \(\dfrac{5}{2}\)xy - \(\dfrac{1}{2}\)y - 1.