Most Important Selected Qs for JEE AdvancedMathematicsQuadratic Equation
If eqautions (a+2) x^2+b x+c=0 and 2 x^2+3 x+4=0 have a common root where a, b, c N then -
Options
- Ab^2-4 a c 0
- Bminimum value of a + b + c is 16
- Cb^2 4 a c+8 c
- Dminimum value of a + b + c =7
Correct answer
C. b^2 4 a c+8 c
Step-by-step solution
(a+2) x^2+b x+c=0 .....(i) 2 x^2+3 x+4=0 ......(ii) for (2) D 0 (i) & (ii) have both roots common. a+2 2 = b 3 = c 4 for equation (1) D 0 aligned & b^2-4 c(a+2) 0 & b^2 4 a c+8 c & a+2 2 = b 3 = c 4 =k( say ) k N, k 2 & a+b+c+2 9 =k & a+b+c=9 k-2 & (a+b+c)_ =16 aligned