`x^2-25=0`

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

`<=>[(x-5=0),(x+5=0):}`

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

Mọi người tham gia đi nè phần thưởng cao á :>

`a)125+214+316`

125 lẻ;214 chẵn;316 chẵn

`=>125+214+316` lẻ nên không chia hết cho 2

`b)136+348+165+17`

136 chẵn;348 chẵn;165 lẻ;17 lẻ

`=>136+348+165+17` chẵn nên chia hết cho 2

`A=-(x^2-2x)-(y^2+6y)+9`

`=-(x^2-2x+1)-(y^2+6y+9)+19`

`=-(x-1)^2-(y+3)^2+19<=19`

Dấu "=" xảy ra khi `x=1` và `y=-3`

`B=-(2x-5)^2+6|2x+5|+4`

`=-[(2x-5)^2-6|2x-5|+9]+13`

`=-(|2x-5|-3)^2+13<=13`

Dấu "=" xảy ra khi `|2x-5|=3<=>[(x=4),(x=1):}`

`5-10-2x=5^7:5^3`

`=>-5-2x=5^4=625`

`=>2x=-630`

`=>x=-315`

`a)x^3-8x^2+16x`

`=x(x^2-8x+16)`

`=x(x-4)^2`

`b)x^2+4y^2+2x-4y-4xy-24`

`=(x-2y)^2+2(x-2y)-24`

`=(x-2y)^2-4(x-2y)+6(x-2y)-24`

`=(x-2y-4)(x-2y+6)`

`c)x^4+x^3-x^2-2x-2`

`=x^4-2x^2+x^3-2x+x^2-2`

`=x^2(x^2-2)+x(x^2-2)+x^2-2`

`=(x^2-2)(x^2+x+1)`

`a)(x-3)^2-x(x-6)`

`=x^2-6x+9-x^2+6x=9`

`b)(2x+1)^2-(3+2x)(2x-3)-4(x+2)`

`=4x^2+4x+1-(4x^2-9)-4x-8`

`=2`

`c)(2x^2-3x+1):(x-1)`

`=(2x^2-2x-x+1):(x-1)`

`=[2x(x-1)-(x-1)]:(x-1)`

`=2x-1`

`5sqrt12-2sqrt48-4sqrt75+3sqrt27`

`=5sqrt{4.3}-2sqrt{16.3}-4sqrt{25.3}+3sqrt{9.3}`

`=10sqrt3-8sqrt3-20sqrt3+9sqrt3`

`=-9sqrt3`

`-x^2+25x-150`

`=-(x^2-25x+150)`

`=-(x^2-10x-15x+150)`

`=-[x(x-10)-15(x-10)]`

`=-(x-10)(x-15)`

100km gấp 2 lần 50k nên ô tô đó đi quãng đường 50km sẽ tiêu thụ:

12:2=6(l)