2t + 1
The area of a rectangle is its length x it’s width/breadth(A = lw) so 20t^2 + 10t = l x w
We know the breadth is 10t cm, so you can plug that in for w.
20t^2 + 10t = 10t x l
Divide each side by 10t to isolate the unknown variable (l).
l = 20t^2/10t + 10t/10t
10t/10t = 1
20t^2/10t: 20/10 = 2, t^2/t = t so 20t^2/10t =2t
l = 2t + 1
You can check this, as A = l x w, so 10t(2t +1) should equal 20t^2 + 10t
10t x 2t = 20t^2, and 10t x 1 = 10t, so 10t(2t+1) = 20t^2 + 10t.
