Home
Class 12
MATHS
Let f(x) =ax^(2) + bx + c and f(-1) lt 1...

Let `f(x) =ax^(2) + bx + c` and `f(-1) lt 1, f(1) gt -1, f(3) lt -4` and `a ne 0`, then

A

(a) a>0

B

(b) a<0

C

(c) Sign of a can't be determined

D

(a) none of the above

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we will analyze the function \( f(x) = ax^2 + bx + c \) using the given conditions. ### Step 1: Write down the conditions from the problem We have three conditions based on the function evaluated at specific points: 1. \( f(-1) < 1 \) 2. \( f(1) > -1 \) 3. \( f(3) < -4 \) ### Step 2: Express each condition in terms of \( a \), \( b \), and \( c \) 1. For \( f(-1) < 1 \): \[ f(-1) = a(-1)^2 + b(-1) + c = a - b + c < 1 \] This can be rearranged to: \[ a - b + c < 1 \quad \text{(Equation 1)} \] 2. For \( f(1) > -1 \): \[ f(1) = a(1)^2 + b(1) + c = a + b + c > -1 \] This can be rearranged to: \[ a + b + c > -1 \quad \text{(Equation 2)} \] 3. For \( f(3) < -4 \): \[ f(3) = a(3)^2 + b(3) + c = 9a + 3b + c < -4 \] This can be rearranged to: \[ 9a + 3b + c < -4 \quad \text{(Equation 3)} \] ### Step 3: Analyze the inequalities Now we have three inequalities: 1. \( a - b + c < 1 \) 2. \( a + b + c > -1 \) 3. \( 9a + 3b + c < -4 \) ### Step 4: Combine the inequalities Let's add Equation 1 and Equation 3: \[ (a - b + c) + (9a + 3b + c) < 1 - 4 \] This simplifies to: \[ 10a + 2b + 2c < -3 \] Dividing the entire inequality by 2 gives: \[ 5a + b + c < -\frac{3}{2} \quad \text{(Equation 4)} \] Now, we will add Equation 2 and Equation 4: \[ (a + b + c) + (5a + b + c) > -1 - \frac{3}{2} \] This simplifies to: \[ 6a + 2b + 2c > -\frac{5}{2} \] Dividing the entire inequality by 2 gives: \[ 3a + b + c > -\frac{5}{4} \quad \text{(Equation 5)} \] ### Step 5: Analyze the results Now we have two new inequalities: 1. \( 5a + b + c < -\frac{3}{2} \) (Equation 4) 2. \( 3a + b + c > -\frac{5}{4} \) (Equation 5) ### Step 6: Subtract Equation 5 from Equation 4 Subtract Equation 5 from Equation 4: \[ (5a + b + c) - (3a + b + c) < -\frac{3}{2} + \frac{5}{4} \] This simplifies to: \[ 2a < -\frac{3}{2} + \frac{5}{4} \] Finding a common denominator (4): \[ 2a < -\frac{6}{4} + \frac{5}{4} = -\frac{1}{4} \] Dividing both sides by 2 gives: \[ a < -\frac{1}{8} \] ### Conclusion Since \( a < -\frac{1}{8} \), we conclude that \( a < 0 \). Thus, the answer is: **Option B: \( a < 0 \)**.

To solve the problem step by step, we will analyze the function \( f(x) = ax^2 + bx + c \) using the given conditions. ### Step 1: Write down the conditions from the problem We have three conditions based on the function evaluated at specific points: 1. \( f(-1) < 1 \) 2. \( f(1) > -1 \) 3. \( f(3) < -4 \) ...
Promotional Banner

Topper's Solved these Questions

  • MONOTONICITY AND MAXIMA MINIMA OF FUNCTIONS

    CENGAGE ENGLISH|Exercise Numerical Value Type|24 Videos
  • MONOTONICITY AND MAXIMA MINIMA OF FUNCTIONS

    CENGAGE ENGLISH|Exercise Single Correct Answer Type|13 Videos
  • MONOTONICITY AND MAXIMA MINIMA OF FUNCTIONS

    CENGAGE ENGLISH|Exercise Exercise|93 Videos
  • METHODS OF DIFFERENTIATION

    CENGAGE ENGLISH|Exercise Single Correct Answer Type|46 Videos
  • MONOTONOCITY AND NAXINA-MINIMA OF FUNCTIONS

    CENGAGE ENGLISH|Exercise Comprehension Type|6 Videos

Similar Questions

Explore conceptually related problems

If f(x)=ax^(2)+bx+c, f(-1) gt (1)/(2), f(1) lt -1 and f(-3)lt -(1)/(2) , then

Using matrix method, find the quadratic defined by f(x) = ax^(2) + bx + c if f(1) = 0, f(2) = -2 and f(3) = -6. Hence find the value of f(-1).

If f(x)=ax^(2)+bx+c and f(-1) ge -4 , f(1) le 0 and f(3) ge 5 , then the least value of a is

If f(x) = ax^(2) + bx + c is such that |f(0)| le 1, |f(1)| le 1 and |f(-1)| le 1 , prove that |f(x)| le 5//4, AA x in [-1, 1]

(af(mu) lt 0) is the necessary and sufficient condition for a particular real number mu to lie between the roots of a quadratic equations f(x) =0, where f(x) = ax^(2) + bx + c . Again if f(mu_(1)) f(mu_(2)) lt 0 , then exactly one of the roots will lie between mu_(1) and mu_(2) . If c(a+b+c) lt 0 lt (a+b+c)a , then

Let f(x)=(x^(2)-2x+1)/(x+3),f i n d x: (i) f(x) gt 0 (ii) f(x) lt 0

Let f(x) = ax^(2) - bx + c^(2), b ne 0 and f(x) ne 0 for all x in R . Then

If f(x) = ax^2+bx+c and f(1)=3 and f(-1)=3, then a+c equals

If f(x^(2) - 4x + 4) = x^(2) + 1 . Find f(1) if f(1) lt 8 .

Let f (x) =ax ^(2) +bx + c,a ne 0, such the f (-1-x)=f (-1+ x) AA x in R. Also given that f (x) =0 has no real roots and 4a + b gt 0. Let p =b-4a, q=2a +b, then pq is:

CENGAGE ENGLISH-MONOTONICITY AND MAXIMA MINIMA OF FUNCTIONS-Multiple correct answers type
  1. Let f(x)=a x^2-b|x|, where aa n db are constants. Then at x=0,f(x) has...

    Text Solution

    |

  2. The function y=(2x-1)/(x-2),(x!=2) is its own inverse decrease at all...

    Text Solution

    |

  3. Let f(x) =ax^(2) + bx + c and f(-1) lt 1, f(1) gt -1, f(3) lt -4 and a...

    Text Solution

    |

  4. If f(x)=x^3-x^2+100x+2002 ,t h e n f(1000)>f(1001) f(1/(2000))>f(1...

    Text Solution

    |

  5. If f^(prime)x=g(x)(x-a)^2,w h e r eg(a)!=0,a n dg is continuous at x=a...

    Text Solution

    |

  6. The value of a for which the function f(x)=(4a-3)(x+log5)+2(a-7)cot(x/...

    Text Solution

    |

  7. Let f(x) = (x^2 - 1)^(n+1) * (x^2 + x + 1). Then f(x) has local extrem...

    Text Solution

    |

  8. Let f(x)=sinx+a x+bdot Then which of the following is/are true? (a) f(...

    Text Solution

    |

  9. The function (sin(x+a))/(sin(x+b)) has no maxima or minima if b-a=npi...

    Text Solution

    |

  10. Consider f(x)=ax^(4)+cx^(2)+dx+e has no point of inflection. Then whic...

    Text Solution

    |

  11. L e tf(x)={((x-1)(6x-1))/(2x-1),ifx!=1/2 0,ifx=1/2 Then at x=1/2, whi...

    Text Solution

    |

  12. In which of the following graphs is x=c the point of inflection? figur...

    Text Solution

    |

  13. Let f(x) be an increasing function defined on (0,oo) . If f(2a^2+a+1)>...

    Text Solution

    |

  14. Let f(x)=(x-1)^4(x-2)^n ,n in Ndot Then f(x) has (a) a maximum at x=1...

    Text Solution

    |

  15. For the cubic function f(x)=2x^3+9x^2+12 x+1, which one of the followi...

    Text Solution

    |

  16. Let f(x)=a5x^5+a4x^4+a3x^3+a2x^2+a1x , where ai ' s are real and f(x)=...

    Text Solution

    |

  17. If f(x)a n dg(x) are two positive and increasing functions, then which...

    Text Solution

    |

  18. An extremum of the function f(x)=(2-x)/picospi(x+3)+1/(pi^2)sinpi(x+3)...

    Text Solution

    |

  19. For the function f(x)=x^4(12(log)e x-7), the point (1,7) is the point...

    Text Solution

    |

  20. Let f(x)=log(2x-x^2)+sin(pix)/2dot Then which of the following is/are ...

    Text Solution

    |