Chapter 2
Introduction to Linear Polynomials
CBSE Class 9
Mathematics Solutions
Educart Mathematics class Class 9 NCERT Exemplar cover
Question:

Let p(x)=ax+bp(x) = ax + b and q(x)=cx+dq(x) = cx + d be two linear polynomials such that:

(A) The graph of p(x)p(x) passes through the points (2,3)(2, 3) and (6,11)(6, 11).

(B) The graph of q(x)q(x) passes through the point (4,1)(4, -1).

(C) The graph of q(x)q(x) is parallel to the graph of p(x)p(x).

Find the polynomials p(x)p(x) and q(x)q(x). Also, find the coordinates of the point where these lines meet the xx-axis.

Answer: Verified

(A) For p(x):2a+b=3p(x): 2a + b = 3 and 6a+b=116a + b = 11.

Subtract: 4a=8a=24a = 8 \Rightarrow a = 2;

then b=34=1b = 3 - 4 = -1.

So, p(x)=2x1p(x) = 2x - 1.

(B) Parallel lines have equal slopes, so c=2c = 2.

q(x)q(x) passes through (4,1)(4, -1):

1=2(4)+dd=9.-1 = 2(4) + d \Rightarrow d = -9.

So, q(x)=2x9q(x) = 2x - 9.

(C) p(x)p(x) cuts xx-axis:

2x1=02x - 1 = 0

x=12(12,0)\Rightarrow x = \frac{1}{2} \Rightarrow \left(\frac{1}{2}, 0\right)

q(x)q(x) cuts xx-axis:

2x9=02x - 9 = 0

x=92(92,0)\Rightarrow x = \frac{9}{2} \Rightarrow \left(\frac{9}{2}, 0\right)

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