HP 33s Scientific manual Type of Equation Result for ‘, 10Entering and Evaluating Equations, Fx ¼

Because many equations have two sides separated by "=", the basic value of an equation is the difference between the values of the two sides. For this calculation, "=" in an equation essentially treated as "ಥ". The value is a measure of how well the equation balances.

The HP 33s has two keys for evaluating equations: ‘and X. Their actions differ only in how they evaluate assignment equations:

„Xreturns the value of the equation, regardless of the type of equation.

„‘returns the value of the equation — unless it's an assignment–type equation. For an assignment equation, ‘returns the value of the right side only, and also "enters" that value into the variable on the left side — it stores the value in the variable.

The following table shows the two ways to evaluate equations.

Type of Equation	Result for ‘		Result for X
Equality: g(x) = f(x)	g(x) – f(x)
Example: x2 + y2 = r2	x2 + y2– r2
Assignment: y = f(x)	f(x) ¼		y – f(x)
Example: A = 0.5 ⋅ b x h	0.5 ⋅ b ⋅ h ¼		A – 0.5 ⋅ b ⋅ h
Expression: f(x)		f(x)
Example: x3 + 1		x3 + 1

¼ Also stores the result in the left–hand variable, A for example.

To evaluate an equation:

1.Display the desired equation. (See "Displaying and Selecting Equations" above.)

2.Press ‘or X. The equation prompts for a value for each variable needed. (If you've changed the number base, it's automatically changed back to base 10.)

3.For each prompt, enter the desired value:

„If the displayed value is good, press g.

„If you want a different value, type the value and press g. (Also see "Responding to Equation Prompts" later in this chapter.)

6–10Entering and Evaluating Equations