Question

 1. tính hợp lí

a, (25/49 x 17/39+22/39x25/49)x41/25              b, 3+3/11+3/23/8+8/11+8/23:9/8-1/3        c, A=2/3x7+2/7x11+2/11x15+......+2/107x111

Answer 1

a)\(\left(\frac{25}{49}+\frac{17}{39}+\frac{22}{39}\times\frac{25}{49}\right)\times\frac{41}{25}\)

\(=\left(\frac{25}{49}+\left(\frac{17}{39}+\frac{22}{39}\right)\times\frac{25}{49}\right)\times\frac{41}{25}\)

\(=\left(\frac{25}{49}+\frac{39}{39}\times\frac{25}{49}\right)\times\frac{41}{25}\)

\(=\left(\frac{25}{49}+1\times\frac{25}{49}\right)\times\frac{41}{25}\)

\(=\left(\frac{25}{49}+\frac{25}{49}\right)\times\frac{41}{25}\)

\(=\frac{50}{49}\times\frac{41}{25}\)

\(=\frac{2050}{1225}\)