$a$) $(x-32):16=48$
$⇔ x-32 = 48.16$
$⇔ x-32 = 768$
$⇔ x = 768+32$
$⇔ x = 800$
Vậy $x=800$.
$b$) $814-(x-305)=712$
$⇔ x - 305 = 814 - 712$
$⇔ x - 305 = 102$
$⇔ x = 102 + 305$
$⇔ x = 407$
Vậy $x=407$.
$c$) $xy - 2x = 5$
$⇔ x(y-2) = 5$
$⇒ x;y-2$ $∈$ `Ư(5)={±1;±5}`
Ta có bảng:
$\left[\begin{array}{ccc}x&-5&-1&1&5\\y-2&-1&-5&5&1\\y&1&-3&7&3\end{array}\right]$
Vậy `(x;y)=(-5;1);(-1;-3);(1;7);(5;3)`.
$d$) `x+(x+1)+(x+2)+...+(x+100)=10100`
`⇔ 101x + (1+2+...+100) = 10100`
`⇔ 101x + \dfrac{101.100}{2} = 10100`
`⇔ 101x + 101.50 = 10100`
`⇔ 101x + 5050 = 10100`
`⇔ 101x = 5050`
`⇔ x = 50`
Vậy `x=50`.
