2.4+4.6+6.8+......... is given
in this 2 progressions are there
1st- 2+4+6+....... 2nd- 4+6+8+.........
here a = 2 d = a₂-a₁ here a = 4 d = 6-4
= 4-2 = 2 = 2
a₂₀ = a+(20-1)2 a₂₀ = a +(20-1)2
= 2+19(2) = 4 + 19(2)
= 2+38 = 4 + 38
a₂₀ = 40 a₂₀ = 42
a₂₀ of 2.4+4.6+6.8+.........= 40×42
= 1680
