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**Polynomials**

*Definition*: Let be real numbers and x is a real variable. Then f(x) = is called a real polynomial of real variable x with coefficients

Examples: is a polynomial

**Degree of a Polynomial:**

Degree of a polynomial is the highest power of the variable in the polynomial.

**Example:**

Degree of is 3 as the maximum power of the variable x is 3.

On the basis of degree, the polynomials are classified as Linear (Degree 1), Quadratic (degree 2), Cubical

(Degree 3), bi-Quadratic (degree 4), and so on.

**Remainder Theorem**

If any polynomial f(x) is divided by (x - a) then f(a) is the remainder.**For example,**

f(x) = x^{2} - 5x + 7 = 0 is divided by x - 2. What is the remainder?

R = f(2) = 2^{2} - 5 × 2 + 7 = 1.

**Factor Theorem**

If (x - a) is a factor of f(x), then remainder f(a) = 0. (Or) if f(a) = 0, then (x - a) is a factor of f(x),**For example,**

When f(x) = x^{2} - 5x + 6 = 0 is divided by x - 2, the remainder f(2) is zero which shows that x - 2 is the factor of

f(x)

**General Theory of Equations**

An equation is the form of a polynomial which has been equated to some real value.**For example:**

2x + 5 = 0, x^{2} - 2x + 5 = 7, 2x^{2} - 5x^{2} + 1 = 2x + 5 etc. are polynomial equations.

**Root or Zero of a polynomial equation:**

If f (x) = 0 is a polynomial equation and f (α) = 0, then α is called a root or zero of the polynomial equation

f(x) = 0.

**Linear Equation Linear Equation with one variable:**

A linear equation is 1

**Quadratic Equations**

Linear equation with two variables:

Ex: 2x + 3y = 0.

We need two equations to find the values of x and y.

If there are n variables in an equation, we need n equations to find the values of the variables uniquely.

Some times, even the number of equations are equal to the number of variables, we cannot find the values of

x and y uniquely.

For example, 3x + 5y = 6

6x +10y = 12

These are two equations, but both are one and the same. So different values of x and y satisfy the equation

and there is no unique solution. It will has infinite number of solutions.

The number of solutions is clearly described below for the set of equations with 2 variables.

These equations can be

1. Inconsistent means have no solution if

2. Consistent and has infinitely many solutions if

3. Consistent and have unique solution if

**Quadratic Equation**

Quadratic Equation in “x” is one in which the highest power of “x” is 2. The equation is generally satisfied by

two values of “x”.

The quadratic form is generally represented by ax^{2} + bx + c = 0 where a ≠ 0, and a, b, c are constants.

For Example:

x^{2} - 6x + 4 = 0

3x^{2} + 7x - 2 = 0

A quadratic equation in one variable has two and only two roots, which are

**Nature of Roots**

The two roots of any quadratic equation always depend on the value of

b^{2} - 4ac called discriminant (D).

D > 0 Real and unequal roots

D = 0 Real and equal

D < 0 Imaginary and unequal

**Sum and Product of roots:**

If α and β are the two roots of ax^{2} + bx + c = 0,

Then sum of roots = α + β =

2

And product of roots = αβ =

**Formation of equation from roots:**

If α and β are the roots of any quadratic equation then that equation can be written in the form

X^{2} − (α + β)X + αβ = 0

i.e. X^{2} - (sum of the roots) X + Product of the roots = 0

**Some Important results**

-----------------------------------------------**Maximum and Minimum value of a Quadratic equation**

The quadratic equation ax^{2} + bx + c = 0 will have maximum or minimum value at x = - b/2a. If a < 0, it has

maximum value and if a > 0, it has minimum value.

The maximum or minimum value is given by

**Ex.2 A and B went to a hotel paid Rs. 84 for 3 plates of Idli and 5 plates of Dosa. Where as B took 5 plates of Idli and 3 plates of Dosa and paid Rs. 76. What is the cost of one plate of Idli.**

**Sol**. 3I + 5D = 84 ……….(1)

5I + 3D = 76 ………(2)

Equation (1) × 3 - equation (2) × 5, we get

16I = 128

⇒ I = 8

Each plate of Idli cost Rs. 8.

**Ex.3 Find the values of x and y from the equations **

**Sol. **

**Ex.4 Find x and y from **

**Sol. **

**Ex.5 Aman won a competition and so he got some prize money. He gave Rs. 2000 less than the half of prize money to his son and Rs. 1000 more than the two third of the remaining to his daughter. If both they got same amount, what is the prize money Aman got?**

**Sol.**

**Ex.6 How many non negative integer pairs (x, y) satisfy the equation, 3x + 4y = 21?**

**Sol. **Since x and y are non negative integers.

Start from x = 0.

If x = 0 or 2, y cannot be integer.

For x = 3, y = 3.

And for x = 7, y = 0.

These two pairs only satisfy the given equation.

**Ex.7 If (x - 2) is a factor of x ^{3} - 3x^{2} + px + 4. Find the value of p.**

**Sol. **Since (x - 2) is a factor, f(2) = 0.

∴ 2^{3} - 3(2^{2}) + (2)p + 4 = 0

⇒ p = 0

**Ex.8 When x ^{3} - 7x^{2} + 3x - P is divided by x + 3, the remainder is 4, then what is the value of P ?**

**Sol. **f(- 3) = 4

∴ (- 3)^{3} - 7(- 3)^{2} + 3(- 3) - P = 4

P = - 103.

**Ex.9 If (x - 1) is the HCF of (x ^{3} - px^{2} + qx - 3) and (x^{3} - 2x^{2} + px + 2). What is the value of ‘q’?**

**Sol. **Since (x - 1) is HCF, it is a factor for both the polynomials.

∴ 1^{3} - p(1)^{2} + q(1) - 3 = 0 ⇒ - p + q = 2

And 1^{3} - 2(1^{2}) + p(1) + 2 = 0

p = - 1

∴ q = 1

**Ex.10 Find the roots of the quadratic equation x ^{2} - x - 12 = 0.**

**Sol. **x^{2} - x - 12 = 0

⇒ x^{2} - 4x + 3x - 12 = 0

x(x - 4) - 3(x - 4) = 0

(x - 4) (x - 3) = 0

⇒ x = 4 or 3. The roots are 4 and 3.

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