Two numbers whose sum is 6 and the absolute value of whose difference is 8 are the roots of the equation
Two numbers whose sum is 6 and the absolute value of whose difference is 8 are the roots of the equation
A) x2 – 6x + 8 = 0
B) x2 – 6x – 7 = 0
C) x2 – 6x + 7 = 0
D) x2 + 6x – 8 = 0
2 Answers
Correct option is (B) x2 – 6x – 7 = 0
Let both numbers are a & b.
\(\because\) Their sum = 6
and absolute value of their difference = 8
i.e., a+b = 6 _____________(1)
& a - b = 8 _____________(2) (Let a > b)
By adding equations (1) & (2), we get
(a+b) + (a - b) = 6+8
\(\Rightarrow\) 2a = 14
\(\Rightarrow\) a = \(\frac{14}2\) = 7
\(\therefore b=6-a\) (From (1))
\(=6-7=-1\)
\(\therefore\) Product of roots = ab
\(=7\times-1=-7\)
\(\therefore\) Required quadratic equation is
\(x^2-\) (Sum of roots) x + Product of roots = 0
\(\Rightarrow x^2-(a+b)x+ab=0\)
\(\Rightarrow\) \(x^2-6x-7=0\)
Hence, required equation is \(x^2-6x-7=0.\)