RO divides the rectangle into two congruent right triangles.
The area of the one triangle is equal half area of the rectangle.
Calculate the area of rectangle:

The area of right triangle:

Use the Pythagorean theorem to calculate the length of RO:

The formula of an area of this right triangle is:

Therefore we have the equation:

Answer: D
Step-by-step explanation:
A seems complicated and doesn’t make an sense while D is simple
2t^2+1
Subtract t^2 from 3t^2 you get 2t^2
which is 2t^2+1 answer
The answer to the question