HP 39G User Manual page 85

Solve the
unknown
variable
Plot the
equation
Solve aplet
5. Solve for the unknown variable (A).
Therefore, the acceleration needed to increase the speed
of a car from 16.67 m/sec (60 kph) to 27.78 m/sec
(100 kph) in a distance of 100 m is approximately 2.47
2
m/s .
Because the variable A in the equation is linear, once
values are substituted into V, U and D, we know that we
need not look for any other solutions.
The Plot view shows one graph for each member of the
selected equation. You can choose any of the variables in
the Numeric view to be the independent variable.
The other variables take on the values assigned to them in
the Numeric view. The current equation is
2 2
V = U + 2AD . With the variable A highlighted, the
Plot view will show two graphs.
One of these is Y = V
Y = 771.7284 . This graph will be a horizontal line. The
other graph will be Y
and D = 100 , or Y =
also a line. The desired solution is the value of A where
these two lines intersect.
6. Plot the equation for variable A.
Select Auto
Scale
2
, with V = 27.78 , or
2
= U + 2AD , with U = 16.67
200A + 277.8889 . This graph is
7-3