Question

[phạm văn khôi nguyên]

72+36x2+24x3+18x4+12x6+168                                             b        1991x1993-1

2+2+4+6+10+.........+68                                                                     1990+1991x1992

Answer 1

[Trần Tiến Pro ✓]

\(\frac{72+36\times2+24\times3+18\times4+12\times6+168}{2+2+4+6+10+.....+60}\)

\(=\frac{72+72+72+72+72+168}{\left(68-2\right):2+1}\)

\(=\frac{72\times5+168}{\left(68+2\right)\times34\div2}\)

\(=\frac{360+168}{1190}=\frac{528}{1190}=\frac{264}{595}\)

\(b\frac{1991\times1993-1}{1990+1991\times1992}\)

\(=\frac{1991\times\left(1993-1\right)-1}{1990+1991\times1990}\)

\(=\frac{1991\times1992-1}{1990+1991\times1992}\)

\(=\frac{1990}{1990}=1\)