B1 :
\(a.\frac{7.2:2\times46,5+1.55\times3\times64}{1+2+3+4+...+28+29+30}\)
\(b.\frac{1}{2\left(1+2\right)}\)\(+\frac{1}{2\left(1+2+3\right)}\)\(+\frac{1}{2\left(1+2+3+4\right)}\)\(+...+\frac{1}{2\left(1+2+3+4+5+6+7+8+9\right)}\)
* Có thắc mắc gì về đề bài thì ib em ạ ~!!!