HP HP-20S - Quadratic Equation (qUAd)

ap,," ap’ a;y 1 0 O
Inverse and Identity: A-1 = lay ay ay|, I =10 1 0
ay," asy’ asy 0 0 1
where the ith column of the inverse is calculated by solving the sys-
tem of equations with B replaced by the ith column of I.
Quadratic Equation (qUAd)
This program uses the quadratic formula to solve for the real and
complex roots of a second-degree polynomial in the form ax? + bx +
¢ = 0. If two real roots exist, the program first calculates the root with
the larger absolute value, then the root with the smaller absolute
value. If only complex roots exist (when b?> — 4ac < 0), the program
calculates both the real and imaginary parts of the roots.
The program uses R, through Rs.
Program Instructions:
1. Press (%] to enter Program mode, (€] E to load the
program, and (9] to exit Program mode.
2. Enter a and press A.
3. Enter b and press B.
4. Enter ¢ and press C.
5. To calculate the roots, press D.
B If the : annunciator does not come on, the displayed number
is the first real root. Press to see the second real root.
B If the ! annunciator comes on, the displayed number is the
value of the imaginary part of the complex root. Press
(9] (SWAP] to see the real part of the complex root. The second
complex root is the same as the first except for the sign of the
imaginary part.
102 7: Built-in Program Library