Question

What is the area of this triangle? ​

Answer 1

Answer:

D.

Step-by-step explanation:

The formula of an area of a triangle:

$A=\dfrac{1}{2}bh$

b - base

h - height

Look at the picture.

The formula of a distance between two points on a vertical line:

$d_v=(y_2-y_1)$

The formual of a distance between two points on a horizontal line:

$d_h=(x_2-x_1)$

Calculate the lengths of b and h:

$b=(y_2-y_1)\\\\h=(x_3-x_1)$

Substiute to the formula of an area:

$A=\dfrac{1}{2}(y_2-y_1)(x_3-x_1)$

Answer 2

Check the picture below.