Weird Things I think     
by Eric Shepard

Kingdom of Heaven

September 4, 2003

I got an email from my dad. He sends stupid jokes everyday along with some helpful (although they are sometimes not that interesting) tips, and other miscellaneous stuff. Usually I skim through these. Sometimes I delete them before I read them. This one caught my eye:

Jesus and his disciples were walking around one day, when Jesus said, "The Kingdom of Heaven is like 3x squared plus 8x minus 9."

The disciples looked very puzzled, and finally asked Peter, "What on earth does Jesus mean -- 'the Kingdom of Heaven is like 3x squared plus 8x minus 9?'"

Peter said, "Don't worry, guys. It's just another one of his parabolas."

"The Kingdom of Heaven is like 3x squared plus 8x minus 9."

This brought me back to a wonderful time in my life when I was learning calculus. Calculus was by far the funnest subject ever invented... and it is truly a bummer that I don't remember more of it.

Now I wonder why the author of this joke (my dad does not make them up... he just copies them from somewhere) picked 32 + 8x - 9 as the parabola as opposed to say x2 + x + 1 ... or one of the infinite number of parabolas that are out there. Maybe the secret of the universe is in that simple formula.

This particular parabola looks like an "U" (well, a parabolic shaped "U" anyway).

Short of like this: 


At x = 0, its value is -9

When it crosses zero, x=-3.51915 or x=.85248

The slope of the curve at any point on the curve is 6x + 8,
so when it crosses 0, its slopes will be either + 13.11488 or -13.11488 (did I mention that parabolas are very symmetrical?)

Its vertex (point at which the slope is 0 .. or in this case the low point of the valley of the "U" ) is at x= -4/3.
As x approaches infinity, so does the parabola's value.

We can find the area under the curve by evaluating x3 + 4 x2 - 9x at two points on the curve.

This is what the kingdom of God is like.

Now, back to calculus.

(editor's note:  04/29/05 ... I am sure Mr. Shepard had great insightful plans to analyze this, but "Now, back to calculus." was the end of what he wrote.  Maybe some day he will continue his thoughts... but for now, let us know if you have thoughts)
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