Factorization: 9999 * 2-1111 times 27 divided by 102 times 98 cry for help

Factorization: 9999 * 2-1111 times 27 divided by 102 times 98 cry for help

(9999*2-1111*27)/(102*98)
=9999(2-3)/(102*98))
=-9999/((100+2)(100-2)))
=-9999/(100^2-2^2))
=-9999/9996

Simple calculation by using decomposition factor: (1) 57 * 99 + 44 * 99-99

57*99+44*99-99=99(57-1+44)
=99*(56+44)
=99*100
=9900

4 / 1 * 3 + 4 / 3 * 5 + 4 / 5 * 7 + 4 / 7 * 9 + 4 / 9 * 11 +. + 4 / 19 * 21 calculation method

The original formula is 4 (1 / 1 * 3 + 1 / 3 * 5 +...) +1/19*21)
=4/2(1-1/3+1/3-1/5+… +1/19-1/21)
=2(1-1/21)
=40/21