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TS EAMCET · Maths · Quadratic Equation

If y=x2+14x+9x2+2x+3x, then the interval of maximum length in which y lies is

  1. A -5, 4
  2. B -4, 5
  3. C 13, 3
  4. D -13, 3
Verified Solution

Answer & Solution

Correct Answer

(A) -5, 4

Step-by-step Solution

Detailed explanation

Given y=x2+14x+9x2+2x+3 ⇒y(x2+2x+3)=x2+14x+9 ⇒(y-1)x2+2(y-7)x+3y-9=0 We know that for real values of x, D≥0 ⇒4(y-7)2-4(y-1)(3y-9)≥0 ⇒−2y2−2y+40≥0 ⇒y2+y−20≤0 ⇒y2+5y−4y−20≤0…