Question about Casio FX-115ES Scientific Calculator

# How to solve rational equations on my casio fx 115es calculator?

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9(X) = 90 (1+1.5X)/ 1= 0.5X

Posted on Jun 19, 2011

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• Casio Master

Hello,
You must first eliminate the denominators by reducing the different expressions to the same denominators. Use the distributivity property of multiplication to expand your terms. Gather similar monomials. Do all the cleaning to reduce your equation to one of the 2 types that the calculator can handle.[Mode][5:EQN] [3: ax2+bx+c] or [4:ax3+bx2+cx+d]

Remember :Any solution that makes one of the original denominators equal 0 must be rejected.

Hope it helps.

Posted on Sep 12, 2009

• k24674 Sep 16, 2009

Suppose you cleaned the denominators and ended up with a quadratic equation aX^2+bX+c=0. ( a =3., b=-5.2, c= 1.8)

Press [MODE] [5:EQN][3:aX^2+bX+c=0]. It takes you to a screen that shows a b c and under each one there is a place where to enter the value. While the place under a is highlighted you do 3 [=]. The number is put under a and the highlight moves to below b. Then [(-)]5.2 [=] takes the value of b and the highlight moves under c. 1.8 [=] enters the value for c.

Now, when the values of the coefficients` a, b,c are all in press [=].

The screen shows X1= and the result is at the bottom. Thus the first root (solution) is X1=1.255396793.

To get the second solution (a`quadratic equation can have up to 2 real solutions) you press [=] a second time. The screen displays on the top line and to the left X2=. On the bottom line, and to the right, it shows 0.4779365403. This is the value of the second solution.

If you press [=] another time you are taken back to the screen where you enter the values of the coefficients a,b, and c. If you give new values to a,b, c you will solve another quadratic equation.

For a cubic equation [MODE][5:EQN] [4: aX^3 + bX^2+cX+d= 0] takes you to the entry screen where you give the values of a, b, c. Now you must enter the value for d, but you do not see where to enter it. Use the [RightArrow] to uncover where you enter the value of d. You type the value and Press [=][=] to get X1, another [=] displays X2, and a third [=] displays X3.

Be careful, if one of the coefficients is negative, as in the exemple above, you use the (-) key and not the [ - ] key.

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## Related Questions:

### I want to solve an complex equation on casio fx-570 ES Plus

Your scientific calculator is unable to solve complex equation with complex coefficients. You should try to solve by hand directly using the quadratic formula or by factoring the polynomial in z
failing that, another way would be to set z=x+iy, substitute this for z, carry out the algebra and try to separate real and imaginary parts. But your two equations will constitute a system of two quadratic equations. I am not aware of any general method to solve coupled nonlinear equations.
Good luck.

Dec 20, 2012 | Casio FX-115ES Scientific Calculator

### How do i calculate my rational equations using my casio fx-115es for example x/8=8/x

You do not need a calculator for this proportion.
For a proportion a/b=c/d, the product of the extrems (a*d) is equal to the product of the means (b*c).
In your case x*x=8*8 or x^2=64.
The two solutions are x=+square root (64) or x=-square root(64).

For a less trivial equation, you can use the solve feature of the FX-119ES. To do so, use the ALPHA keyboard to enter your equation; once the equation is typed in, do not press the main equal sign, but the Solve key (the key is located near the top left corner of the keyboard). You will be prompted to solve for X?.

Feb 24, 2012 | Casio FX-115ES Scientific Calculator

### How do I solve for y, 2y + (y-3)=18 - 2 (y+3). with the casio fx-300es? and if I cant whats the calculator that will. thanx

Do you really need a calculator to solve a linear equation?
Let us see how to solve it without a calculator.
Remove the parentheses fronm the second term on the left : y-3
Use the distributive property on the last term on the right side -2y-6
Take the term -3 to the right side, changing its sign in the process (becomes +3)
Take the -2y term to the left making it +2y.
3y +2y=18+3-6 or 5y=15 and the answer is straightforward .

As to your Casio FX300ES, it cannot solve equations because it does not have an EQUATION calculation mode. The Casios FX-115ES and FX-991ES have an Equation Mode. If you use any of the two to solve an equation in one variable (linear, quadratic or other) the unknown is taken to be x by default. You would have to change the name of the variable from y to x.

Sep 08, 2011 | Casio fx-300ES Calculator

### Solving linear equations in 3 variables by matrix method in casio fx-115ES

Press key Mode, first select option 5:EQN (by pressing key 5), then option 2: a_nX+b_nY+c_nZ=d_n (by pressin 2).
Now input coefficients from equations in table (each column is for one variable), just type in number and press =, then use arrows to move to another cell.

Sep 02, 2011 | Casio FX-115ES Scientific Calculator

### How do I get the fx-115es to solve this equations 2(4a-9)+3=5a-6

You type in this equation (you enter letter A by pressing ALPHA and then 1st button in 4th row, and you enter = by pressing ALPHA and then CALC). Finally you press SHIFT and then CALC.

Apr 14, 2011 | Casio FX-115ES Scientific Calculator

### How can I solve linear and non-linear equations

Set Computational mode to EQN by pressing [MODE][5:EQN]

Select the type of equations you want to solve

Select the relevant otion and get ready to type in the coefficients (the a's, the b's, the c's etc`.)

For more general non-linear equations, use the SOLVE feature.

Feb 11, 2011 | Casio FX-115ES Scientific Calculator

### I can't plug in "i" on my casio fx-115ES even when

By default the calculator only works with real numbers. To use complex numbers, press MODE 2 to switch to complex mode.

Dec 13, 2010 | Casio FX-115ES Scientific Calculator

### How do i solve a matrix?

What do you mean by "solve a matrix"? Find the inverse? Find the determinant? Find the solution to a system of linear equations? Within limits the fx-115ES can do any of these and more.

The procedures are described in the "Matrix Calculations" section of the manual. If you still have problems, please reply to this post specifying what you want to do.

Nov 18, 2010 | Casio FX-115ES Scientific Calculator

### How do i calculate limits on my Casio fx-115es? Ex. lim x->3 for (x2'-0)/x-3

Sorry, but you cannot calculate limits of functions with this calculator. It does not have a Computer `Algebra System (CAS). For that you need a graphing calculator with CAS: Casio ClassPad 300, 300PLUS, 330, HP 48 GII, HP49 G/ G+, HP 50G, TI-NSPIRE CAS, TI89 Titanium, TI 92/92PLUS, TI Voyage 200 PLT. It is still a very good scientific (non graphing) calculator
However, you can calculate numerical derivatives, and numerical integrals, solve linear and non-linear equations.

Even though this post does meet your expectations, do not let that prevent you from rating it.

Jan 21, 2010 | Casio FX-115ES Scientific Calculator

### Finding Rational Zeros of Polynomials on a Casio FX-115 Sci. Calc.

I'm not sure how to do x4,
but from -5x3 and on yes. Mode-5-4, and insert coefficients.

Here the solution:
1. 1.927
2. -0.413
3. -2.514

Nov 08, 2008 | Casio FX-115ES Scientific Calculator

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