HP50g: solve quadratic equations

Question

How would you solve a quadratic equation on the HP50g? I already know how to use the normal algebraic solver, but I can't solve x^2+2x+1=0, for example. Also, when I hit EXPAND ((x+2)*(x-2)), like the integrated help forum says, it doesn't come up with the solution set. It comes up with -9.9999999E499, which is obviously not the correct answer. How do I change both of these?

Answer 1

Hi,
There are several ways to find the roots.
Method 1:
A useful method is to use the numerical solver:
Red-Right-Shift    NUM.SLV  (on 7 key), then choose "3. Solve poly.."
Enter the vector of coefficents, e.g. for x^2+2x+1=0 enter [1,2,1] then with Roots section highlighted, choose F6 SOLVE
Answer is [-1 -1]
for example x^2-4=0 enter [1,0,-4]
Answer is [-2 -2]
Method 2a:
Another method is to use the SOLVE command, White-Left-Shift   S.SLV, 6.SOLVE (or F6 SOLVE if using soft menus).
In RPN mode:
'X^2-4'
'X'
SOLVE
Answer: {X=-2 X=2}
Algebraic mode:
SOLVE(X^2-4,X)
Answer: {X=-2 X=2}
Method 2b:
As a shortcut you can use SOLVEVX command, White-Left-Shift   S.SLV, 5.SOLVEVX (or F5 SOLVEVX if using soft menus).
With this command, the current active variable is assumed to be soved for (indicated on the top of the screen, usually 'X'). You then do not need to specify the variable to solve for.
In RPN mode:
'X^2-4'
SOLVEVX
Answer: {X=-2 X=2}
Algebraic mode:
SOLVEVX(X^2-4)
Answer: {X=-2 X=2}
Please see page 3-229 & 3-230 in the Advanced User's Reference Manual (v2) for notes and flag settings for the various SOLVE commands.
You can download the Advanced User's Reference Manual (v2) from this web page:
http://h10025.www1.hp.com/ewfrf/wc/manualCategory?cc=us&dlc=en&lc=en&product=3235175&
(section 3 of this reference details each command of the 50g)
Hope this helps.
Note: I do not work for HP, I just like playing with calculators :-)