28×57+14×50
=28×57+28×25
=28×(57+25)
=28×82
=(8×8+2×2)×10+2×8×101★
=680+1616
=2296
公式
(10a+b)(10b+a)
=10(a²+b²)+101ab
28×57+14×50
=28×57+14×2x25
=28×57+(14x2)x25
=28×57+28x25
=28x(57+25)
=28x82
=28x(100-18)
=28x100-28x18
=2800-28x(20-2)
=2800-28x20+28x2
=2800-560+56
=2240+56
=2296
14乘以50等于28乘以25。用提公因式法,先用50加25,得75,再用14乘以75,得1050,它就是最终结果了。28×57+14×50
=7×228+7×100
=7×(228+100)
=7×328
=2296