正确求解 由题设得X~N(20,0.3),Y~N(20,02) X-Y~N(0,0.5) P(Xx-y>03)=1-P(x-y503) =1-P(-0.3≤X-y≤0.3) =1-(0.3√2)+①(0.32) 2-2(0.3√2)=0.6744正确求解 由题设得 X ~ N ( 20, 0.3), Y ~ N ( 20, 0.2) X −Y ~ N (0, 0.5) P( X −Y  0.3) =1− P( X −Y  0.3) =1− P(− 0.3  X −Y  0.3) =1−(0.3 2 ) + (−0.3 2) = 2 − 2(0.3 2 ) = 0.6744