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## Another Method to Solve Inequality with Casio fx991es

Linear Inequality
​​​​​​(1). Find the inequalities 2X + 15 < 31
(a). X < 8 (b). X < 6 (c). X < 4
(NB: < is minus for linear Inequality, > is plus for linear Inequality, = is either plus or minus for quadratic Inequality, < or equals to is either plus or minus for quadratic Inequality, > or equals to is either plus or minus for quadratic Inequality)
Make X any number in the option and if it gives zero as the answer the option is correct.
Solution Using Casio fx991es.
Checking Option A
(NB: Use brackets to separate the left hand side before the less than sign and use brackets to separate the right hand side after the less than sign)
Make X = 8
[ON] [8] [SHIFT] [STO] [X] [AC] [(] [2] [ALPHA] [X] [+] [1] [5] [)] [-] [(] [3] [1] [)] [=]
Option A is correct it gives zero as the answer.

(2). Solve the Inequalities 2X - 3 < X + 7
(a). X < 10 (b). X < 8 (c). X < 6
Checking Option A
Make X = 10
Solution Using Casio fx991es
[ON] [1] [0] [SHIFT] [STO] [X] [(] [2] [ALPHA] [X] [-] [3] [)] [-] [(] [ALPHA] [X] [+] [7] [)] [=]
Option A is correct it gives zero as the answer.

Quadratic Inequality
(3). Find the solution set of the inequality (X - 1) (X + 4) < 0
(a). -4 < X < 1 (b). 4 < X < - 1 (c). -1 < X < 4
In this case you pick each number from the option and make it X and if it gives zero as the answer the option is correct.
Checking Option A
Make X = -4
Solution Using Casio fx991es
[ON] [-] [4] [SHIFT] [STO] [X] [AC] [(] [(] [ALPHA] [X] [-] [1] [)] [(] [ALPHA] [X] [+] [4] [)] [)] [-] [(] [0] [)] [=]
It gives answer as zero it is correct.
Make X = 1
Solution Using Casio fx991es
[ON] [1] [SHIFT] [STO] [X] [AC] [(] [(] [ALPHA] [X] [-] [1] [)] [(] [ALPHA] [X] [+] [4] [)] [)] [-] [(] [0] [)] [=]
It gives zero as the answer it is correct.
Therefore Option A is correct.

(4). Solve the equation (3X - 2) = 10
(a). 4 and -8/3 (b). 2 and -4/3 (c). -4 and 2/3
Choose any number in the option and if it gives zero as the answer then the option is correct.
Checking Option A
Make X = 4
Solution Using Casio fx991es
[ON] [4] [SHIFT] [STO] [X] [AC] [(] [3] [ALPHA] [X] [-] [2] [)] [-] [(] [1] [0] [)] [=]
In this case I tried plus it didn't give zero as the answer then I tried minus and it gives zero as the answer therefore it is correct.
Make X = -8/3
Solution Using Casio fx991es
[ON] [-] [8] [÷] [3] [=] [SHIFT] [STO] [X] [AC] [(] [3] [ALPHA] [X] [-] [2] [)] [+] [(] [1] [0] [)] [=]
In this case I tried minus it didn't give zero as the answer then I tried plus and it gives zero as the answer, Therefore Option A is correct.
You can go ahead and try other Option to see if it is correct.

(5). Find the solution set of the inequalities X² - 3X + 2 > 0
(a). 1 < X < 2 (b) -1 < X < -2 (c). -2 < X < -3
Choose any number in the option and if it gives zero as the answer then the option is correct.
Checking Option A
Make X = 1
Solution Using Casio fx991es
[ON] [1] [SHIFT] [STO] [X] [AC] [(] [ALPHA] [X] [X²] [-] [3] [ALPHA] [X] [+] [2] [)] [+] [(] [0] [)] [=]
In this case I used plus sign it gives zero as the answer and I used minus sign it still gives zero as the answer so both of them are correct.
Make X = 2
Solution Using Casio fx991es
[ON] [2] [SHIFT] [STO] [X] [AC] [(] [ALPHA] [X] [X²] [-] [3] [ALPHA] [X] [+] [2] [)] [-] [(] [0] [)] [=]
In this case I used plus it gives zero as the answer and I used minus it still gives zero as the answer, so you can use any of them both of them are correct as far as it gives zero as the answer. Therefore Option A is correct.
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