Earth has a radius of about 6.4 x 106 m. a.) Approximate the surface area of Earth using the formula for the surface area of a sphere, S=4πr2. b) Earth’s surface is about 70% water, almost all of it in oceans. About how many square meters of Earth’s surface are covered with water? c) The oceans have an average depth of 3795 m. Estimate the volume of water on Earth.

Slope-intercept form is , where  is the slope and is the y-intercept.

Slope = -3, y-intercept = -1

Plug in what we know:





Slope = -2, y-intercept = -4

Plug in what we know:





Through: (-3,2) , slope=-1/3

Okay, here we use point-slope form, and the simplify to get it in slope-intercept form.



Where is the y-value of the point, is the x-value of the point, and is the slope.

Plug in what we know:



Distribute -1/3 into the parenthesis:



Add 2 to both sides:



Through: (3,2) and (0,-5)

Now we plug this into the slope-formula to find the slope, plug the slope and one of these points into point-slope form, then simplify to get it in slope-intercept form.



(3, 2), (0, -5)
x1 y1 x2  y2

Plug in what we know:



Subtract:





Plug this into point-slope form along with any point.





Distribute 7/3 into the parenthesis:



Add 2 to both sides:



x-5y-5=0

Add 5 to both sides:



Subtract 'x' to both sides:



Divide -5 to both sides: