(1/11+1/20+1/31+1/40）*（1/21+1/30+1/41+1/50)-(1/11+1/21+1/31+1/41+1/51）*（1/21+1/31+1/41)=? | Math enthusiast | Mathematical art

(1/11+1/20+1/31+1/40）（1/21+1/30+1/41+1/50)-(1/11+1/21+1/31+1/41+1/51）（1/21+1/31+1/41)=?

Is the title wrong?
Is the title like this:
(1/11+1/21+1/31+1/41）*（1/21+1/31+1/41+1/51)-(1/11+1/21+1/31+1/41+1/51）*（1/21+1/31+1/41)
Let a = 1 / 21 + 1 / 31 + 1 / 41
The original formula = (1 / 11 + a) * (a + 1 / 51) - (1 / 11 + A + 1 / 51) * a
=a/11+a²+1/11*51+a/51-a/11-a²-a/51
=1/561

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