\(a,\left(5x-3\right)\left(3x+1\right)-\left(15x+1\right)\left(x-2\right)=0\)

\(\Rightarrow\left(15x^2-4x-3\right)-\left(15x^2-29x-2\right)=0\)

\(\Rightarrow15x^2-4x-3-15x^2+29x+2=0\)

\(\Rightarrow25x-1=0\) 

\(\Rightarrow x=\dfrac{1}{25}\)

\(----------\)

\(b,x^2+\left(x+5\right)\left(x-3\right)-25=0\)

\(\Rightarrow x^2+x^2+2x-15-25=0\)

\(\Rightarrow2x^2+2x=40\)

\(\Rightarrow2x\left(x+1\right)=40\)

\(\Rightarrow x\left(x+1\right)=20\)

\(\Rightarrow x;x+1\) là ước của 20

mà \(x;x+1\) là hai số nguyên liên tiếp \(\left(x\in Z\right)\)

nên \(x\left(x+1\right)=4.5=\left(-5\right).\left(-4\right)=20\)

\(\Rightarrow x\in\left\{4;-5\right\}\)

a: =>15x^2+5x-9x-3-15x^2+30x-x+2=0

=>25x-1=0

=>x=1/25

b: =>x^2+x^2+2x-15-25=0

=>2x^2+2x-40=0

=>x^2+x-20=0

=>(x+5)(x-4)=0

=>x=4 hoặc x=-5

-5(3x-7) - ( -15x+3) - ( 12 -x ) =-4

=>-15x+35+15x-3-12+x=-4

=>20+x=-4

=>x=-4-20

=>x=-24

-3(4x-2) - ( -12+8) - (-x)=0

=>-12x+6+12-8+x=0

=>-11x+10=0

=>-11x=0-10

=>-11x=-10

=>11x=10

=>x=10:11=\(\frac{10}{11}\)

a   x=5-3

x=2

b   15x+11=101

    15x=101-11

    15x=90

       x = 90:15

      x  = 6

c    x+2=0

    x=0-2

  x=-2

a: =>(x+5)(3x-2)=0

=>x=-5 hoặc x=2/3

b: Đề thiếu rồi bạn

c: \(\Leftrightarrow x^2-4x-5=0\)

=>(x-5)(x+1)=0

=>x=5 hoặc x=-1

a) Ta có: \(7x\left(x-20\right)-x+20=0\)

\(\Leftrightarrow\left(x-20\right)\left(7x-1\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=20\\x=\dfrac{1}{7}\end{matrix}\right.\)

b) Ta có: \(x^3-15x=0\)

\(\Leftrightarrow x\left(x-\sqrt{15}\right)\left(x+\sqrt{15}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{15}\\x=-\sqrt{15}\end{matrix}\right.\)