`2x-3y=1`

`<=>3y=2x-1`

`<=>x=(2x-1)/3` thay vào pt dưới ta có:

`x^2-x*(2x-1)/3=24`

`<=>x^2-2x^2/3+x/3=24`

`<=>x^2/3+x/3=24`

`<=>x^2+x-72=0`

`<=>(x-8)(x+9)=0`

`<=>[(x=8),(x=-9):}`

`<=>[({(x=8),(y=5):}),({(x=-9),(y=-19/3):}):}`

`a)A=2011.2013`

`=(2012-1)(2012+1)`

`=2012^2-1<2012^2=B`

`b)A=4(3^2+1)(3^4+1)...(3^64+1)`

`A=(3+1)(3^2+1)(3^4+1)...(3^64+1)`

`2A=(3-1)(3+1)(3^2+1)(3^4+1)...(3^64+1)`

`2A=(3^2-1)(3^2+1)(3^4+1)...(3^64+1)`

...

`2A=3^128-1=B`

`=>A<B`

`3/4x-1/2=3/7`

`3/4x=1/2+3/7`

`3/4x=13/14`

`x=13/14:3/4`

`x=26/21`

`d)(1-x)^3+x(x+2)^2-(x+5)=0`

`<=>1-3x+3x^2-x^3+x^3+4x^2+4x-x-5=0`

`<=>7x^2-4=0`

`<=>x^2=4/7`

`<=>x=+-2/sqrt7`

`e)(x-3)^3-(x-3)(x^2+3x+9)+9(x+1)^2=15`

`<=>(x-3)(x^2-6x+9-x^2-3x-9)+9(x^2+2x+1)=15`

`<=>(x-3).(-9x)+9x^2+18x+9=15`

`<=>-9x^2+27x+9x^2+18x-6=0`

`<=>45x-6=0`

`<=>x=2/15`

`f)x(x-5)(x+5)-(x+2)(x^2-2x+4)=3`

`<=>x(x^2-25)-(x^3+8)=3`

`<=>x^3-25x-x^3-8-3=0`

`<=>-25x-11=0`

`<=>x=-11/25`

`11/12-(2/5+x)=2/5`

`11/12-2/5-x=2/5`

`x=11/12-2/5-2/5`

`x=11/12-4/5`

`x=7/60`

Vậy `x=7/60`

`a)(4x+1)^2-(4x+5)(4x-5)=2x+3`

`<=>(4x)^2+2.4x+1-(4x)^2+25=2x+3`

`<=>16x^2+8x+1-16x^2+25=2x+3`

`<=>6x+26=3`

`<=>6x=-23`

`<=>x=-23/6`

`b)(x+3)(x^2-3x+9)-x(x+1)^2=5x`

`<=>x^3+27-(x^3+2x^2+x)=5x`

`<=>27-2x^2-x=5x`

`<=>2x^2+6x-27=0`

`<=>x=(-3+-3\sqrt7)/2`

`c)(2x-1)(2x+1)-4(x+6)^2=3(x-4)`

`<=>4x^2-1-4(x^2+12x+36)=3x-12`

`<=>-48x-145=3x-12`

`<=>51x=133`

`<=>x=-133/51`

`3/3-(3/5+x)=2/7`

`1-3/5-x=2/7`

`2/5-x=2/7`

`x=2/5-2/7`

`x=4/35`

`1A=3x(5x^2-4)+x^2(8-15x)-8x^2(|x|=3)`

`A=15x^3-12x+8x^2-15x^3-8x^2`

`A=-12x=[(-36(x=3)),(36(x=-3)):}`

`B=x^3(x^2-y^2)+y^2(x^3-y^3)(x=2,|y|=1)`

`B=x^5-x^3y^2+x^3y^2-y^5`

`B=x^5-y^5`

`B=[(32-1=31(x=2,y=1)),(32+1=33(x=2,y=-1)):}`

`5/12-(-3/8-x)=-5/6`

`<=>5/12+3/8+x=-5/6`

`<=>x=-5/6-5/12-3/8`

`<=>x=-13/8`

Vậy `x=-13/8`

`2x-3>2y-3`

`<=>2x-3+3>2y-3+3`

`<=>2x>2y`

`<=>x>y`