For what values of m can the expression 2x2 + mxy + 3y2 - 5y - 2

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

If F is function such that F (0) = 2, F(1) = 3, F(x + 2)= 2F(x) - F(x + 1) for x > 0, then F(5) is equal to

  • - 7

  • - 3

  • 17

  • 13


2.

Let S be a set containing n elements. Then, number of binary operations on S is

  • nn

  • 2n2

  • nn2

  • n2


3.

The numerically greatest term in the expansion of (3 - 5x)11 when x = 15, is

  • 55 × 39

  • 55 × 36

  • 45 × 39

  • 45 × 36


4.

The number of solutions of the equation sin(ex) = 5x + 5-x,  is

  • 0

  • 1

  • 2

  • infinitely many


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5.

If ax = by = cz = du and a, b, c, d are in GP, then x, y, z, u are in

  • AP

  • GP

  • HP

  • None of these


6.

If z satisfies the equation z - z = 1 + 2i, then z is equal to

  • 32 + 2i

  • 32 - 2i

  • 2 - 32i

  • 2 + 32i


7.

If z = 1 - i31 + i3, then arg (z) is

  • 60°

  • 120°

  • 240°

  • 300°


8.

If f (x) = log10x2. The set of all values of x for which f(x) is real, is

  • [- 1, 1]

  • [1, )

  • (- , - 1]

  • (- , - 1]  [1, )


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9.

For what values of m can the expression 2x2 + mxy + 3y2 - 5y - 2 be expressed as the product of two linear factors?

  • 0

  • ± 1

  • ± 7

  • 49


C.

± 7

We have the expression

2x2 + mxy + 3y- 5y - 2

Comparing the given expression with

ax2 + 2hxy + by2 + 2gx + 2fy + c,

we get

a = 2, h = m2, b = 3, c = - 2, g = 0, f = - 52

The given expression is resolvable into linear factors, if 

abc + 2fgh - af2 - bg2 - ch2 = 0

(2) (3) (- 2) + 2(0) - 2254 - 0 - (- 2)m24 = 0

 - 12 - 252 + m22 = 0                         m22 = 492                          m2 = 49                           m = ± 7


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10.

If 3sinθ + 5cosθ, then the value of 5sinθ - 3cosθ is equal to

  • 5

  • 3

  • 4

  • None of these


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