tính nhanh :
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/7x9x11 + 4/9x11x13 .
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/7x9x11 + 4/9x11x13
tính nhanh 4/1x3x5+4/3x5x7+4/5x7x9+4/7x9x11+4/9x11x13
\(\dfrac{4}{1x3x5}+\dfrac{4}{3x5x7}+\dfrac{4}{5x7x9}+\dfrac{4}{9x11x13}\)
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/7x9x11 + 4/9x11x13 . Tính nhanh nhé
tính nhanh :
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/ 7x9x11 + 4/9x11x13
\(A=\frac{3x5x7+6x10x14+9x15x21}{5x7x9+10x14x18+15x21x27}\)
4/1x3x5 + 4/3x5x7 + 4/5x7x9 + 4/7x9x11 + 4/9x11x13
2.1991/1990 x 1992/1991 x 1993/1992 x 1994/1993 x 1995/997
ai lam dung minh tick
Chứng minh rằng:A=36/1x3x5+36/3x5x7+36/5x7x9+....+36/25x27x29