数学学霸帮帮忙
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31415926²-31415927x31415925
=31415926²-(31415926+1)(31415926-1)
=31415926²-31415926²+1
=1
20.09x62+200.9x3.9-7x2.87
=20.09x(62+39)-20.09
=20.09x(101-1)
=2009
223x7.5+22.3x12.5+230÷4-0.7x2.5+1
=22.3x(75+12.5)+230x0.25-0.7x2.5+1
=22.3x87.5+(223+7)x0.25-0.7x2.5+1
=22.3x87.5+223x0.25+7x0.25-0.7x2.5+1
=22.3x(87.5+2.5)+7x(0.25-0.25)+1
=22.3x(100-10)+1
=2230-223+1
=2008
1.25x17.6+36÷0.8+2.64x12.5
=1.25x17.6+36x1.25+2.64x12.5
=1.25x(17.6+36+26.4)
=1.25x80
=100
(7.88+6.87+6.02)(9.87+10.88+10)-(7.88+6.87+6.02+10)(9.87+10.88)
=10x(7.88+6.87+6.02-9.87-10.88)
=10x0.02
=0.2