HP 15c Scientific 000–, 002–, 003–, 004–, G G r, Display, Example:, Solution:, 001–42,21,11, Keystrokes |¥

Begin with label.

184 Section 13: Finding the Roots of an Equation

You have now found the two roots of f(x)

=0. Note that this quadratic equation could have been solved algebraically – and you would have obtained the same roots that you found using _.

G G r

The convenience and power of the _ key become more apparent when you solve an equation for a root that cannot be determined algebraically.

Example: Champion ridget hurler Chuck Fahr throws a ridget with an upward velocity of 50 meters/second. If the height of the ridget is expressed as

h = 5000(1 – e–t/20) – 200t,

how long does it take for it to reach the ground again? In this equation, h is the height in meters and t is the time in seconds.

Solution: The desired solution is the positive value of t at which h = 0.

Use the following subroutine to calculate the height.

Keystrokes ¥

´bA

2

0

÷

Display

000–001–42,21,11

002– 2 Subroutine assumes t is loaded in X-and Y-registers.

003– 0

004– 10