`(x-3/2)^2 = 4`

`<=>` \(\left[{}\begin{matrix}x-\dfrac{3}{2}=2\\x-\dfrac{3}{2}=-2\end{matrix}\right.\)

`<=>` \(\left[{}\begin{matrix}x=3,5\\x=-0,5\end{matrix}\right.\)

Nếu `sqrt(x-3) in I -> A in I ->` Vô lý.

`-> sqrt(x-3) in ZZ`.

`-> 5 vdots sqrt(x-3)`

`-> sqrt(x-3) in Ư(5)`.

`-> x in {4, 7, 28}`.

`3,5 MB= 28 xx 10^6 bit`.

Gọi số bé là `overline(ab)`, số lớn là `overline(1ab)`.

`-> overline(ab) + overline(1ab) = 214`

`10a + b + 100 + 10a +b = 214`

`20a + 2b = 114`

`10a + b = 57`

`overline(ab) = 57`.

`overline(1ab) = 157`.

`5x + 9 vdots x + 3`

`5x + 15 - 6 vdots x+3`

`5(x+3) - 6 vdots x +3`

`6 vdots x + 3`

`x + 3 in Ư(6)`.

`-> x in {-2, -4, -1, -5, 0, -6, 3, -9}`

`= 648 xx (1125 - 111 - 13) - 648`

`= 648 xx 1001 - 648`

`= 648 xx 1000`

`= 648 000`

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

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

`a, = 5(x^2-2xy+y^2-4z^2)`

`= 5((x-y)^2 - 4z^2)`

`= 5((x-y+z)(x-y-z))`.

`b, (x+y)(x^2-xy+y^2) -(x+y)`

`= (x+y)(x^2-xy+y^2-1)`.

`c, (2x+1)^2 - y^2`

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

Theo NTBS, NT Bán bảo toàn và khuôn mẫu.