\(\left(19x+2,25\right)\div14=\left(13-8\right)^2-4\)
\(\left(19x+\frac{9}{4}\right)\div14=\left(13-8\right)^2-4\)
\(\left(19x+\frac{9}{4}\right)\div14=5^2-4\)
\(\left(19x+\frac{9}{4}\right)\div14=25-4\)
\(\left(19x+\frac{9}{4}\right)\div14=21\)
\(\left(19x+\frac{9}{4}\right)=21\times14\)
\(\left(19x+\frac{9}{4}\right)=294\)
\(19x=294-\frac{9}{4}\)
\(x=\frac{1167}{4}\div19\)
\(x=\frac{1167}{76}\)
\(1+2+3+4+...+x=378\)
\(\left(1+x\right)\cdot x\div2=378\)
\(\left(1+x\right)\cdot x=378\times2\)
\(\left(1+x\right)\cdot x=756\)
\(\left(1+x\right)\cdot x=28\cdot27\)
\(\Rightarrow x=27\)
c
\(x+5⋮2x-1\)
\(2x+10⋮2x-1\Leftrightarrow2x-1+11⋮2x-1\)
\(\Leftrightarrow11⋮2x-1\)
\(2x-1\inƯ\left(11\right)=\left\{1;11;-1;-11\right\}\)
\(\Rightarrow x\in\left\{1;6;0;-5\right\}\)
Lập bảng ra cho dễ nhé
b)
Số số hạng : x
Tổng \(\frac{\left(x+1\right)x}{2}=378\)
\(x\left(x+1\right)=756\)
\(x=\orbr{\begin{cases}-27\\28\end{cases}}\)
