99x99+199
=99x99+99+100
=99x(99+1)+100
=99x100+100
=100x(99+1)
=10000
(100-1)*99+199
=9900-99+199
=9900+199-99
=9900+100
=10000
99*99+199=99*99+99+100
=99*(99+1)+100
=99*100+100
=100*(99+1)
=100*100
=10000
99*99+199=(100-1)(100-1)+(100-1)+100
=(100-1)(100-1+1)+100
=(100-1)*100+100
=9900+100
=10000