Casio FX-991ES PLUS Equation Solve Calculator Tutorial Animation

Solving equations is possible with the equation solver in the fx-991ES PLUS calculator’s shift-solve functionality. Once the equation has been entered, the calculator uses the Newton-Raphson numerical method to solve the equation. Because the equation solver uses a numerical method, it only works with equations with a single variable.

For example, I will solve the following equation for x.

  1. Begin by entering the left expression normally, using X for the variable that you wish to solve.
  2. Use = (accessible through ALPHA CALC, then enter the right expression.
  3. shift-solve to enter equation solve by pressing SHIFT CALC. Solve for X will be shown on screen.
  4. If applicable, enter a number as the starting point for the Newton-Raphson numerical method solving for x. The current value of X is displayed for reference and will be used if no new value is provided.
  5. Press = to begin solving the equation.

The first value of x as found by the numerical method will be provided on the screen and is saved to the X variable. The difference between the left expression and the right expression is shown as the solution to L–R.

Caveats: As mentioned, this only works with equations with one variable. The variable can be used multiple times, as shown in this example, however you can’t use two or more variables such as x and y. If you wish to use more than one variable, you need to use the quadratic equation solve. Furthermore, the Newton-Raphson numerical method only returns one value. To find another value, change the start point at step 4. For example, if there are two solutions, one positive and one negative, and you find the positive one, enter a negative number for the start point to find the negative answer.

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1 klmmm’s avatar

Is it possible to use variables to get an answer like this; 105+a+2a (press equals and then) 50+3a?

0 David Nyan’s avatar

Can I use sin and cos in the equations? And how can I use 2 variables with 2 equations?

0 Charbel Chahine’s avatar

how to get both answer of the equation of second degres ? using solvw

0 Arslan Iftikhar’s avatar

√x^2-3x+36 -√x^2-3x+9 =3 how to solve this equation fx991es-plus

0 Iryna Dymkar’s avatar

My calculator always gives the same result when I do equation solver operations. What do I have to do?

0 mhdshbzshrf’s avatar

after typing my eqution and pressing ‘solve’ , why do they ask “Solve for X” ?

what should I do there ?

typing in any no. as a reply to the above (Solve for X) couldn’t always bring me the correct answer!

0 محمد عمران’s avatar

thanks it works for me.

0 ahmed nauman’s avatar

how to get an answer inthe foem of x like (x-2)(x-0)=x2-2x

0 VAIBHAV GUPTA’s avatar

My CalC does nothing after shift solve

0 A.Bharat Karki’s avatar

Wait for some time…My calculator takes some time for difficulat ones…

0 reanakua’s avatar

it should be in 1-Comp mode

i wasnt able to use it with 2-cmplx

0 Chothiru Wagachchi’s avatar

How to get M in the display?

0 Lorie Mae Fabia Bautista’s avatar

this is y question too, how do I get M on display? the little big M at the upper beside S and A

0 Abdul Razak’s avatar

How can i solve equations with variables on both sides on 991es plus

Been at it for hours now

0 Dhruvi Patel’s avatar

How can I simplify an equation, like simplify/add/subtract a polynomial. ex; -h^6 + 4h^5 -3h^4 + 2h^5 -9h^6. This would be simplified as 6h^5 – 10h^6 – 3h^4. How would you simplify that on a calculator


How can I solve quartiles using 991ES PLUS? Thanks.

0 gauti’s avatar

can this method give two values of x (if applicable) ?

0 Priyamvada Arte’s avatar

How do I solve problems like 111/88 on the calculator? It doesn’t calculate in decimals

0 omarpit26’s avatar

calculate the fraction and then click on the S< ->D button just above DEL

0 Piyush Singh’s avatar

Can I solve Trigonometric equations like tan(x)=x ?

0 Paige’s avatar

No matter what function I enter, my solver always says X=1.666591966×10^(-5) … anyway I can fix it?

0 Bobby’s avatar

you have to hit “solve” and then the “=”. Then it has a loading thingie and then spits out an answer.