3.96-2.89+3.96+2.89和5.82-2.27+3.18-0.73该怎样简便计算?

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3.96-2.89+3.96+2.89和5.82-2.27+3.18-0.73该怎样简便计算?
3.96-2.89+3.96+2.89和5.82-2.27+3.18-0.73该怎样简便计算?

3.96-2.89+3.96+2.89和5.82-2.27+3.18-0.73该怎样简便计算?
3.96-2.89+3.96+2.89
=3.96×2+(2.89-2.89)
=(4-0.04)×2+0
=4×2-0.04×2
=8-0.08
=7.92
5.82-2.27+3.18-0.73
=(5.82+3.18)-(2.27+0.73)
=9-3
=6

由题意
f(-x)中有-2<=-x<=4
-4<=x<=2
而f(x)中是-2<=x<=4
要同时满足
-2<=x<=2
定义域[-2,2]
√63+√28
=3√7+2√7
=5√7
选C

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