Solved CAT Questions (Algebra) - Set 5


  • Skadoooosh!!!


    Q1. (CAT 2000)
    Each of the number x1, x2, x3 ... xn (n > 4) is equal to 1 or -1.
    Suppose x1x2x3x4 + x2x3x4x5 + x3x4x5x6 + .... + x(n-1)xnx1x2 + xnx1x2x3 = 0. then
    a) n is even
    b) n is odd
    c) n is an odd multiple of 3
    d) n is prime

    We can see that total number of terms in the given expression is n.
    Now to get a sum of 0 there should be PAIRS of 1 and -1.
    So n should be even.

    Q2. (CAT 1999)
    0_1490169119881_q55.png

    G(f(x, y)) + F(f(x, y) = 0 -- (1)
    as f (x, y) = | x + y |
    f(x, y) = f(-x, -y)
    So d satisfies.

    Q3. (CAT 1997)
    Log_2 [ Log_7 (x^2 - x + 37) ] = 1, then what could be the value of x ?
    a) 3
    b) 4
    c) 5
    d) None of these

    Log_2 [ Log_7 (x^2 - x + 37) ] = 1
    => Log_7 (x^2 - x + 37) = 2^1
    => x^2 - x + 37 = 7^2 = 49
    => x^2 - x - 12 = 0
    x = 4

    Q4. (CAT 1997)
    If roots p and q of the quadratic equation x^2 - 2x + c = 0 also satisfy the equation 7q - 4p = 47, then which of the following is true
    a. c = -15
    b. p = -5, q = 3
    c. p = 4.5, q = -2.5
    d. None of these

    p + q = 2
    7q - 4p = 47
    solve and we have, p = -3 and q = 5
    c = p x q = -15

    Q5. (CAT 1996)
    Which of the following values of x do not satisfy the equation x^2 - 3x + 2 > 0 at all.
    a. 1 ≤ x ≤ 2
    b. -1 ≥ x ≥ 2
    c. 0 ≤ x ≤ 2
    d. 0 ≥ x ≥ 2

    On solving x^2-3x+2>0 , we get (x-1)(x-2)>0
    That is the roots are x = 1 or x = 2
    The equation assumes a positive value for all values which belong to the interval less than 1 and greater than 2
    For x = 1 and x = 2, it becomes zero and for any value of x between 1 and 2 it becomes negative.
    So, option a


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