28 x 34 - 17 x 56 + 1000
= 28 x 34 - 17 x 2 x 28 + 1000
= 28 x 34 - 34 x 28 + 1000
= 28 x (34 - 34) + 1000
= 28 x 0 + 1000
= 0 + 1000 = 1000
28x34-17x56+1000=28x17x2-17x56+1000=17x(28x2-56)+1000=17x0+1000=1000
Ta có : 28x34-17x56+1000=28x17x2-17x28x2+1000=0+1000=1000
78,56 * 34,5+ 13,5*78,56+78,56+52