Evaluate an expression for a value of x
Find the value of 3x² − 2x + 1 when x is 4.
To evaluate means to put a number in place of the letter and work out the result. With x = 4, 3x² − 2x + 1 becomes 3 × 16 − 8 + 1 = 41.
Classic Graphing 84
Start on the main screen: Press 2nd then mode (QUIT) to get back to the home screen. Pressing clear on a menu also backs out of it.
Store 4 in X: type 4, press sto→, then the X,T,θ,n key, and enter.
4sto→X,T,θ,nenterType the expression using the X key and press enter.
3X,T,θ,nx²−2X,T,θ,n+1enter
You should see4→X 3X²−2X+1 41
Natural Scientific 991
Start on the main screen: Press MENU, then 1 (Calculate) to return to the main calculation screen. AC clears the line you are on.
Store 4 in x: type 4, press SHIFT then RCL (STO), then ALPHA and the x key (the close-bracket key). Press =.
4SHIFTSTORCLALPHAx)=Type 3x² − 2x + 1 using ALPHA x each time. Press =.
3ALPHAx)x²−2ALPHAx)+1=
You should see3x²−2x+1 41
Classic CAS
Start on the main screen: Press home to open the Home menu (Calculator, Graphs, Settings, and more). Choose Calculator, or press esc to go back to the calculation page.
Store 4 in x with ctrl and the var key, then x. Press enter.
4ctrlsto→varxenterType the expression using the x key and press enter.
3xx²−2x+1enter
You should see4→x 3x²−2x+1 41
RPN Scientific 15
Start on the main screen: There is no menu to leave. Press the back arrow to clear a number you are typing, or CLx (g then back arrow) to clear the X register.
RPN has no letters, so store x = 4 in register 1.
4STO1Rewrite the expression as ((3x − 2)x + 1), which needs fewer keys. Key in 3, recall x, multiply, subtract 2, recall x, multiply, add 1.
3RCL1×2−RCL1×1+
You should see41.0000
Tips
- Put brackets around a negative value: for x = −2, type (−2)² not −2².