Find the area of the triangle.
A. 73.6ft^2
B. 65.8 ft^2
C. 69.1 ft^2
D. 70.8 ft^2

a) In a coordinate plane, the horizontal axis is the x-axis, and the vertical axis is the y-axis.

So, a point (x, y) is at:

A horizontal distance of x units from the origin.

A vertical distance of y units from the origin.

So the point (3, -7) is at:

3 units at the right from the origin

7 units downwards (because is a -7) from the origin.

The graph of the point can be seen below:

Now we want to find a reflection across the x-axis.

b) For a general point (x, y), a reflection across the x-axis gives:

(x, -y)

So, if our point P is:

P (5, 1)

The reflection across the x-axis just changes the sign of the y-value, which gives:

(5, -1)

Then the correct option is point C:

(5, -1)