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Introduction to Linear Polynomials - Exploring linear patterns

Grade 9CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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A polynomial of degree 11 is called a linear polynomial. The highest power of the variable in such a polynomial is 11.

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The standard form of a linear polynomial in one variable xx is p(x)=ax+bp(x) = ax + b, where aa and bb are real numbers and a≠0a \neq 0.

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A value kk is called a zero of the polynomial p(x)p(x) if p(k)=0p(k) = 0. For a linear polynomial ax+bax + b, there is exactly one zero.

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Linear polynomials are used to represent linear patterns or sequences where the difference between consecutive terms is constant. If the common difference is dd and the first term is a1a_{1}, the nn-th term can be expressed as a linear expression in nn.

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Geometrically, the graph of a linear polynomial y=ax+by = ax + b is always a straight line.

📐Formulae

p(x)=ax+b,a≠0p(x) = ax + b, \quad a \neq 0

Zero of p(x)=−ba=−constant termcoefficient of x\text{Zero of } p(x) = -\frac{b}{a} = -\frac{\text{constant term}}{\text{coefficient of } x}

General term of a linear pattern: Tn=dn+c\text{General term of a linear pattern: } T_n = dn + c

💡Examples

Problem 1:

Find the zero of the linear polynomial p(x)=5x−15p(x) = 5x - 15.

Solution:

To find the zero, we set p(x)=0p(x) = 0: 5x−15=05x - 15 = 0 5x=155x = 15 x=155x = \frac{15}{5} x=3x = 3

Explanation:

The zero of the polynomial is the value of xx that makes the expression equal to zero. For ax+bax + b, it is always −ba-\frac{b}{a}.

Problem 2:

Consider the sequence 4,7,10,13,…4, 7, 10, 13, \dots. Express this pattern as a linear polynomial in terms of nn, where nn is the position of the term.

Solution:

  1. Find the common difference: 7−4=37 - 4 = 3, 10−7=310 - 7 = 3. So, d=3d = 3.
  2. The general form is Tn=dn+cT_n = dn + c.
  3. Substitute n=1,T1=4n = 1, T_1 = 4: 4=3(1)+c4 = 3(1) + c 4=3+c4 = 3 + c c=1c = 1
  4. The linear expression is Tn=3n+1T_n = 3n + 1.

Explanation:

A sequence with a constant difference represents a linear pattern. The coefficient of nn is the common difference.

Problem 3:

Which of the following are linear polynomials? (i) 2x+32x + 3 (ii) x2−5x^2 - 5 (iii) x+1\sqrt{x} + 1 (iv) 4y4y

Solution:

(i) 2x+32x + 3 is linear (degree 11). (ii) x2−5x^2 - 5 is not linear (degree 22). (iii) x+1\sqrt{x} + 1 is not a polynomial because the power of xx is 12\frac{1}{2}. (iv) 4y4y is linear (degree 11).

Explanation:

A linear polynomial must have a variable with a power of exactly 11 and must satisfy the definition of a polynomial (whole number exponents).