\(x\left(3x-5\right)=0\)

\(\Rightarrow\hept{\begin{cases}x=0\\3x-5=0\end{cases}\Rightarrow\hept{\begin{cases}x=0\\x=\frac{5}{3}\end{cases}}}\)

Vậy \(x\in\left\{0;\frac{5}{3}\right\}\)

a) \(x\left(3x-5\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\3x-5=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{5}{3}\end{cases}}}\)

b) \(3x^2-27=0\)

\(\Leftrightarrow3x^2=27\)

\(\Leftrightarrow x^2=9\)

\(\Leftrightarrow x=\pm3\)

c) \(\left(x-5\right)^2=x-5\)

\(\Leftrightarrow x^2-10x+25-x+5=0\)

\(\Leftrightarrow x^2-11x+30=0\)

\(\Leftrightarrow\left(x-6\right)\left(x-5\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-6=0\\x-5=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=6\\x=5\end{cases}}}\)

d) \(2\left(x+7\right)-x^2-7x=0\)

\(\Leftrightarrow2x+14-x^2-7x=0\)

\(\Leftrightarrow-x^2-5x+14=0\)

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

\(\Leftrightarrow\orbr{\begin{cases}x-7=0\\x-2=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=7\\x=2\end{cases}}}\)

e)\(7x\left(x-3\right)+2.3x=0\)

\(\Leftrightarrow7x^2-21x+6x=0\)

\(\Leftrightarrow7x^2-15x=0\)

\(\Leftrightarrow x\left(7x-15\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x=0\\7x-15=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\frac{15}{7}\end{cases}}}\)

#H

a) 3x+9y

=3(x+3y)

b) 4x²-16xy

=4x(x-4y)

c) x²-6x+9

=(x-3)²

d) 4y²-36

=(2y-6)(2y+6)

e) 4y²-4

=(2y-2)(2y+2)

f) 5a²-9

=\(\left(\sqrt{5}a-3\right)\left(\sqrt{5}a+3\right)\)

g) x³-2x²+x

=x(x²-2x+1)

=x(x-1)²

h) 5xy³-10xy²+5xy

=5xy(y²-2y+1)

=5xy(y-1)²

i) 12x²y+12xy+3y

=3y(4x²+4x+1)

=3y(2x+1)²

k) 5x-5y+y²-xy

=(5x-5y)+(y²-xy)

=5(x-y)-y(x-y)

=(x-y)(5-y)

#H

(x2-11x+28)(x2-7x+10)-72=0

(x-2)(x-7)(x-4)(x-5)-72=0

(x2-9x+14)(x2-9x+20)-72=0

Đặt x2-9x+14=a, ta có

a(a+6)-72=0

a2+6a-72=0

a2+6a+9-81=0

(a+3)2=81

=> a+3=9 => a=6=> x2-9x+14=6

=>x2-9x+8=0

=> (x-1)(x-8)=0

=> x=1 hoặc x=8

Vậy............ !!!!!

Đề là tìm x hay phân tích đa thức thành nhân tử vậy em ơi?

Ô tô từ B trở về A với vận tốc là:

          42 - 12 = 30 (km/h)

Độ dài quãng đường AB là:

          30 . 6 = 180 (km)

               Đáp số: 180 km

rùi sao nx ???????????????

Bài đâu???

\(x^4+y^4=\left(x^2+y^2\right)^2-2x^2y^2=\left[\left(x+y\right)^2-2xy\right]^2-2x^2y^2\)

\(=\left(m^2-2n\right)^2-2n^2=m^4-4m^2n+4n^2-2n^2=m^4-4m^2n+2n^2\)