Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Algebra

Question:
If (x – 1) and (x + 3) are the factors of x2 + k1x + k2 then
Options:
 
k1 = –2, k2 = –3
 
k1 = 2, k2 = 3
 
k1 = –2, k2 = 3
Correct Answer:
Explanation:

f(x) = x2 + k1x + k2

(x – 1) is a factor of f(x) .

∴    f(1) = 0

⇒ 1 + k1 + k2 = 0

⇒ k1 + k2 = –1           ...(i)

Again,

f(–3) = 0    ⇒ (–3)2 + k1(–3) + k2 = 0

⇒ 9 – 3k1 + k2 = 0   ⇒    3k1 – k2 = 9           ...(ii)

On adding both equations,

4k1 = 8

⇒  k1 = 2

From eq.(i) ,

k1 + k2 = –1   ⇒  2 + k2 = –1   

⇒  k2 = –3.