Question
Question: The expression \(\frac{x^{2} + 2x + 1}{x^{2} + 2x + 7}\) lies in the interval (x Ī R)...
The expression x2+2x+7x2+2x+1 lies in the interval (x Ī R)
A
[0, – 1]
B
(–, 1) Č [1, )
C
[0, 1)
D
None of these
Answer
[0, 1)
Explanation
Solution
Let y = x2+2x + 1/x 2 + 2x + 7
Ž x2(1– y) + 2x (1–y)+1–7y = 0, As x is real, so D ³ 0;
i.e. 4(1 – y)2 – 4(1 – y) (1 – 7y) ³ 0;
1 + y2–2y–7y2 + 8y – 1 ³ 0
Ž – 6y2 + 6y ³ 0 = y2 – y £ 0
\ y Ī [0, 1) (As y ¹ 1)