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) p(0)=5p(0) = 5.

(B) The polynomial p(x)q(x)p(x) - q(x) cuts the xx-axis at (3,0)(3, 0).

(C) The sum p(x)+q(x)p(x) + q(x) is equal to 6x+46x + 4 for all real xx.

Find the polynomials p(x)p(x) and q(x)q(x).

Answer: Verified

From (A): p(0)=b=5p(0) = b = 5.

From (B): p(x)+q(x)=(a+c)x+(b+d)p(x) + q(x) = (a + c)x + (b + d)

=6x+4= 6x + 4

a+c=6\Rightarrow a + c = 6 and b+d=4b + d = 4.

Since b=5b = 5, d=45=1d = 4 - 5 = -1.

From (B): p(x)q(x)=(ac)x+(bd)p(x) - q(x) = (a - c)x + (b - d).

At x=3x = 3, value = 0:

3(ac)+(5(1))=03(a - c) + (5 - (-1)) = 0

3(ac)+6=0\Rightarrow 3(a - c) + 6 = 0

ac=2\Rightarrow a - c = -2.

Solve a+c=6a + c = 6 and ac=2a - c = -2: a=2a = 2, c=4c = 4.

Therefore, p(x)=2x+5p(x) = 2x + 5 and q(x)=4x1q(x) = 4x - 1.

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