1、12.065.072.94 30.349.7610.34 3 3 2574 83441.7 1.25 0.8 321027.35.1 17 + -7 7141 9537,a+b+c=a+ (b + c ), a+b-c=a +(b-c), a-b+c=a (b-c), a-b-c= a-( b +c);933-15.7-4.3 41.0619.7220.28 7 3 + 8 +2 -528749511 +7 +3325abc=a(bc), abc=a(bc), abc=a(bc) , abc=a(bc),700145 18.62.50.4 1.960.54 1.062.5413 29 197
2、2713a+ (b + c )= a+b+c a +(b-c)= a+b-c a (b-c)= a-b+c a-( b +c)= a-b-c;19.68(2.682.97) 5.68(5.394.32) 19.68(2.979.68) 7 +( - ) 128575 -( - )76831a(bc) = abc, a(bc) = abc, a(bc) = abc , a(bc) = abc,1.25( 8 0.5) 0.25( 4 1.2) 1.25( 2130.8) 9.3(4 ) 0.74(71 )9310107424( - - + ) (12+ ) 7 (7 - )128367253201980.921.410.928.59 - 161.311.61.61.3 11.618.459599999+999+99+9 4821-9983.212.525 1.2588 3.60.25 7.60.25 3.50.1257.6 417.64。1.8991.8 3.89.90.38 103- 2- 1.019.62572571020.87 2.69.9 31+ + 327 172351736 3837 3713.527+13.572+13.5 1.57.4+0.6150%+2 325.3 +2.725% 0.6710.16.7 412821.62.816 5.61.70.5683