`(3x-5)^4=256`

`=>(3x-5)^4=(4)^4=(-4)^4`

`=>[(3x-5=4),(3x-5=-4):}`

`=>[(3x=9),(3x=1):}`

`=>[(x=3),(x=1/3):}`

Vậy `x=3` hoặc `x=1/3.`

`(x-1)^2-25=0`

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

`<=>(x-6)(x+4)=0`

`<=>[(x-6=0),(x+4=0):}`

`<=>[(x=6),(x=-4):}`

Vậy `x=6` hoặc `x=-4`

`a)5/9:(1/11-5/22)+5/9:(1/15-2/3)`

`=5/9:(2/22-5/22)+5/9:(1/15-10/15)`

`=5/9:(-3)/22+5/9:(-9)/15`

`=5/9*(-22)/3+5/9*(-5)/3`

`=5/9*(-22/3+(-5)/3)`

`=5/9*(-9)=-5`

`4x^2-1=0`

`<=>(2x-1)(2x+1)=0`

`<=>[(2x-1=0),(2x+1=0):}`

`<=>[(2x=1),(2x=-1):}`

`<=>[(x=1/2),(x=-1/2):}`

Vậy `x=1/2` hoặc `x=-1/2`

`sqrt{4x-4}+sqrt{9x-9}-2sqrt{25x-25}+15=5(x>=1)`

`<=>2\sqrt{x-1}+3sqrt{x-1}-10sqrt{x-1}+15=5`

`<=>-5sqrt{x-1}=5-15=-10`

`<=>sqrt{x-1}=2`

`<=>x-1=4<=>x=5(tm)`

Vậy `x=5`

`A=x^2-4x+y^2-8y+6`

`A=x^2-4x+4+y^2-8y+16-14`

`A=(x-2)^2+(y-4)^2-14`

VÌ `(x-2)^2+(y-4)^2>=0`

`=>(x-2)^2+(y-4)^2-14>=-14`

`=>A>=-14`

Dấu "=" xảy ra khi `x-2=0,y-4=0<=>{(x=2),(y=4):}`

`(4x-1)^3=27`

`=>(4x-1)^3=3^3`

`=>4x-1=3`

`=>4x=4=>x=1`

Vậy `x=1`

`a)5x(x-1)-(x+2)(5x-7)=6`

`<=>5x^2-5x-(5x^2-7x+10x-14)=6`

`<=>5x^2-5x-(5x^2+3x-14)=6`

`<=>-8x+14=6`

`<=>8x=8<=>x=1`

Vậy `x=1`

`b)(x+2)^2-(x^2-4)=0`

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

`<=>4x+8=0`

`<=>4x=-8`

`<=>x=-2`

Vậy `x=-2`

`4x^2+4x+1=0`

`<=>(2x)^2+2.2x+1=0`

`<=>(2x+1)^2=0`

`<=>2x+1=0`

`<=>2x=-1`

`<=>x=-1/2`

Vậy `x=-1/2.`