Can someone plz me with this maths question

199,500

Step-by-step explanation:

First you  set up proportion equation. Since 210,000 is the whole it goes on the bottom of the the equation and x goes on top because that is what we are trying to find. Now for the percent it will go on top and 100 will go the bottom (this goes for any proportion equation the percent will always be on top of 100). Next you cross cross multiply that means you times 210,000 by 5 to get 1,050,000 and then 100 by X which you can't do so you divide 1,050,000 by 100 to get 10,500 but we are not done here we now need to subtract it by 210,000  to get 199,500.

aₙ = 2*n*n - n -1

Step-by-step explanation:

a₁ = 0

a₂ = 5 = 2*2*2 -2-1 = 8-3 = 5

a₃ = 2*3*3 -3-1 = 18-4 =14

a₄ = 2*4*4 - 4-1 = 32-5 =27

aₙ = 2*n*n - n -1