f1 := (x^2 -y^2)*(exp(-k*R*(x+y)))/(x-y);

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f2 := int(f1,y=-1..1);

NiM+SSNmMkc2IiooLC4qKi1JJGV4cEc2JEkqcHJvdGVjdGVkR0YsSShfc3lzbGliR0YlNiMsJCooSSJrR0YlIiIiSSJSR0YlRjIsJkkieEdGJUYyISIiRjJGMkY2RjJGMUYyRjNGMkY1RjJGMkYpRjIqKEYpRjJGMUYyRjNGMkY2KiotRio2IywkKihGMUYyRjNGMiwmRjJGMkY1RjJGMkY2RjJGMUYyRjNGMkY1RjJGNkY5RjYqKEY5RjJGMUYyRjNGMkY2RjJGMSEiI0YzRj8=

int (f2,x=1..inf);

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f3 := ((x^2 -y^2)/(x-y))*exp(-k*R*x);

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f4:= int (f3,y=-1..1);

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int(f4,x=1..inf);

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