Đáp án:
Giải thích các bước giải:
$2x+7$ $\vdots$ $x+1$
$⇒2x+2+5$ $\vdots$ $x+1$
$⇒2.(x+1)+5$ $\vdots$ $x+1$
$⇒5$ $\vdots$ $x+1$
$⇒x+1=${$5;1;-1;-5$}
$⇒x=${$4;0;-2;-6$}
$2.$
$(x+1)+(x+2)+...+(x+100)=5750$
$⇒x+1+x+2+x+3+...+x+100=5750$
$⇒(x+x+....+x)+(1+2+3+...+100)=5750$
$⇒100x+(100+1).\frac{(100+1):1+1}{2}$=$5750$
$⇒100x+101.50=5750$
$⇒100x+5050=5750$
$⇒100x=700$
$⇒x=7$