What you have showed us is an equation for a surface. There would be no
intersection.
Try to give us the actual problem without assuming the z-function.
For example, you might have an equations
y1 = 2x+ 5 for manufacturing cost where x is products made, and
y2 = 3x-6 for profit where x is units sold.
A plot of these would cross at x = 11
But note we would plot TWO functions not ONE

best wishes
--
Bernard V Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme
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wrote in message
...
Can Excel graph the following equation? If so, how would I go about
doing this?

z=((.03y+.15)x+150.75)x

Basically, I have a different cost formula for each of 4 different
suppliers. All have a different twist, but all contain the same 2
variables (x and y) and result in a single value (z). I need to be
able to graph the equations so that I can visually present where the
costs intersect.