How to find the area of the rectangular region 2 ≤ x ≤ 5, -1 ≤ y ≤ 3

Question

How to find the area of the rectangular region $2 ≤ x ≤ 5$, $-1 ≤ y ≤ 3$.

I tried to plot the graph in $xy$-plane, but I'm not sure how to find the area.

Answer 1

Area of a rectangle is given by base$\times$height. The base of this rectangle is the change in $x=|5-2|=3$ and the height of the rectangle is the change in $y=|3-(-1)|=4$. The area is then $$3\times4=12$$

Answer 2

The area of a rectangle of length $L \times l$ is $L\cdot l$.

One of the lengh $L_x$ is equal to the interval of variation of x: $L_x = 5-2 = 3$.

Same goes for $L_y = 3 - (-1) = 3 + 1 = 4$

The area is $3\cdot 4 = 12$.