Question

A = 1/15 + 1/35 + 1/63 + 1/99 + ... + 1/9999

A = ?

Nêu cách làm giùm!

Answer 1

A=1/15 + 1/35 + 1/63 + 1/99 + ... + 1/9999

A= 1/3x5 + 1/5x7 + 1/7x9 + 1/9x11 + ...+ 1/99x101

Ax2= 2/3x5 +  2/5x7 + 2/7x9 + 2/9x11 + ... + 2/99x101

Ax2= 5-3/3x5 + 7-5/5x7 + 9-7/7x9 + 11-9/9x11 + ... + 101-99/99x101

Ax2=5/3x5 - 3/3x5 + 7/5x7 - 5/5x7 + 9/7x9 -7/7x9 + ... + 101/99x101 -99/99x101

Ax2=1/3 - 1/5 + 1/5 - 1/7 + 1/7 - 1/9 + ... + 1/99 - 1/101

Ax2= 1/3 - 1/101

Ax2 = 98/303

A= 98/303 : 2

A=49/303

Answer 2

Ôi xin lỗi ! Đừng quên tick nha