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Algebra

Cube roots and other roots

Find any root of a number, such as the cube root of 27.

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The cube root of 27 asks: which number multiplied by itself three times makes 27? The answer is 3. Roots are the opposite of powers.

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.

  1. Type the root number 3 first, open the MATH menu and choose item 5, the x-th root symbol.

    3math5

  2. Type 27 and press enter.

    27enter

You should see3ˣ√27 3

Classic Graphing 84 key reference

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.

  1. Press SHIFT then the power key to get the root template. Type 3 as the root, press right, then type 27.

    SHIFT√x3▶27

  2. Press =.

    =

You should see3√(27) 3

Natural Scientific 991 key reference

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.

  1. Press ctrl then the power key for the root template. Type 3, press right, then 27.

    ctrlⁿ√^3▶27

  2. Press enter.

    enter

You should see3√(27) 3

Classic CAS key reference

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.

  1. A cube root is the same as raising to the power one third. Key in 27 and press ENTER.

    27ENTER

  2. Key in 3, press 1/x to get one third, then press yˣ.

    31/xyˣ

You should see3.0000

RPN Scientific 15 key reference

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