`a. 5x(x-2000)-x+2000=0`
`<=>5x(x-2000)-(x-2000)=0`
`<=>(x-2000)(5x-1)=0`
`<=>[(x-2000=0),(5x-1=0):}`
`<=>[(x=0+2000),(5x=0+1):}`
`<=>[(x=2000),(5x=1):}`
`<=>[(x=2000),(x=1:5):}`
`<=>[(x=2000),(x=1/5):}`
Vậy, `x\in{2000; 1/5}`
`b. x^3-13x=0`
`<=>x . (x^2-13)=0`
`<=>[(x=0),(x^2-13=0):}`
`<=>[(x=0),(x^2-(\sqrt{13})^2=0):}`
`<=>[(x=0),((x-\sqrt{13})(x+\sqrt{13})=0):}`
`<=>[(x=0),([(x-\sqrt{13}=0),(x+\sqrt{13}=0):}):}`
`<=>[(x=0),([(x=0+\sqrt{13}),(x=0-\sqrt{13}):}):}`
`<=>[(x=0),([(x=\sqrt{13}),(x=-\sqrt{13}):}):}`
Vậy, `x\in{0; \sqrt{13}; -\sqrt{13}}`
`c. x^2(x-3)+12-4x=0`
`<=>x^2(x-3)-4x+12=0`
`<=>x^2(x-3)-(4x-12)=0`
`<=>x^2(x-3)-4(x-3)=0`
`<=>(x^2-4)(x-3)=0`
`<=>[(x^2-4=0),(x-3=0):}`
`<=>[(x^2-2^2=0),(x-3=0):}`
`<=>[((x-2)(x+2)=0),(x-3=0):}`
`<=>[([(x-2=0),(x+2=0):}),(x-3=0):}`
`<=>[([(x=0+2),(x=0-2):}),(x=0+3):}`
`<=>[([(x=2),(x=-2):}),(x=3):}`
Vậy, `x\in{2; -2; 3}`
`d. x(x-2)+x-2=0`
`<=>x(x-2)+(x-2)=0`
`<=>(x+1)(x-2)=0`
`<=>[(x+1=0),(x-2=0):}`
`<=>[(x=0-1),(x=0+2):}`
`<=>[(x=-1),(x=2):}`
`e. 5x(x-3)-x+3=0`
`<=>5x(x-3)-(x-3)=0`
`<=>(5x-1)(x-3)=0`
`<=>[(5x-1=0),(x-3=0):}`
`<=>[(5x=0+1),(x=0+3):}`
`<=>[(5x=1),(x=3):}`
`<=>[(x=1:5),(x=3):}`
`<=>[(x=1/5),(x=3):}`
Vậy, `x\in{1/5; 3}`
`f. (2x-1)^2-(x+3)^2=0`
`<=>4x^2-4x+1-(x^2+6x+9)=0`
`<=>4x^2-4x+1-x^2-6x-9=0`
`<=>(4x^2-x^2)-(4x+6x)+(1-9)=0`
`<=>3x^2-10x-8=0`
`<=>3x^2+2x-12x-8=0`
`<=>(3x^2+2x)-(12x+8)=0`
`<=>x(3x+2)-4(3x+2)=0`
`<=>(x-4)(3x+2)=0`
`<=>[(x-4=0),(3x+2=0):}`
`<=>[(x=0+4),(3x=0-2):}`
`<=>[(x=4),(3x=-2):}`
`<=>[(x=4),(x=(-2):3):}`
`<=>[(x=4),(x=-2/3):}`
Vậy, `x\in{4; -2/3}`
`g. x^2-x+1/4=0`
`<=>x^2-2 . x . 1/2+(1/2)^2=0`
`<=>(x-1/2)^2=0`
`<=>(x-1/2)^2=0^2`
`<=>x-1/2=0`
`<=>x=0+1/2`
`<=>x=1/2`
Vậy, `x=1/2`
`h, x^3-1/4x=0`
`<=>x(x^2-1/4)=0`
`<=>[(x=0),(x^2-1/4=0):}`
`<=>[(x=0),(x^2-(1/2)^2=0):}`
`<=>[(x=0),((x-1/2)(x+1/2)=0):}`
`<=>[(x=0),([(x-1/2=0),(x+1/2=0):}):}`
`<=>[(x=0),([(x=0+1/2),(x=0-1/2):}):}`
`<=>[(x=0),([(x=1/2),(x=-1/2):}):}`
Vậy, `x\in{0; 1/2; -1/2}.`
