The equation solver

21.1Solve an equation for a variable#

Open the solver with math, then ▲ (which wraps to the last item, B: Solver…), then enter. Type an expression that equals zero, such as X²−4, or an equation with an equals sign, such as X²=9, and press enter. The solver lists the variables. Type a guess in the variable you want to find, then press alphaSOLVEenter (SOLVE). The answer is marked with a black square, and left−rt shows how close the two sides are (0 means an exact solution).

Example 21.1

Solve x² − 4 = 0

$$x^{2}-4=0$$

1. Open the solver, type X²−4 and press enter.

   math▲enterX,T,θ,nx²−4enter

   

2. Type 1 as a guess and press alpha enter.

   1alphaSOLVEenter

Example 21.2

The other solution comes from another guess

1. Same equation, guess −1.

   math▲enterX,T,θ,nx²−4enter(−)1alphaSOLVEenter

Example 21.3

An equation with an equals sign

$$x^2=9$$

1. Type X²=9 using 2nd math then 1 for the equals sign.

   math▲enterX,T,θ,nx²2ndTESTmath19enter1alphaSOLVEenter

Example 21.4

Solve for a different variable

$$AB-12=0,\ B=3\Rightarrow A=4$$

1. Type A*B−12. Move down to B and type 3, move up to A and press alpha enter.

   math▲enteralphaAmath×alphaBapps−12enter▼3▲alphaSOLVEenter

Example 21.5

The answer is stored in the variable

1. Solve 2X−5 = 0 with the default guess.

   math▲enter2X,T,θ,n−5enteralphaSOLVEenter

2. Go home and type X.

   2ndQUITmodeX,T,θ,nenter