72.Find the discriminant of the following quadratic equations, and hence find the nature of its roots.
x2 + x + 1 = 0 Here, a = 1, b = 1, c = 1 Now, D = b2 – 4ac = (1)2 – 4(1) (1) = 1 – 4 = –3 Since, D < 0 Therefore, given quadratic equation has no real roots.
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73.For what value of A, are the roots of the quadratic equation 3x2 + 2kx + 27 = 0 real and equal?
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74.For what value of A, are the roots of the quadratic equation: kx2 + 4x + 1 = 0 equal and real?
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Long Answer Type
75.For what value of A, does (k – 12)x2 + 2 (k – 12)x + 2 = 0 have equal roots?
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Short Answer Type
76.For what value of A, does the equation 9x2 + 3kx + 4 = 0 have equal roots?
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Long Answer Type
77.If (–5) is a root of the quadratic equation 2x2 + px – 15 = 0 and the quadratic equation p(x2 + x) + k = 0 has equal roots, then find the values of p and A.
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78.If one of the roots of the quadratic 2x2 + px – 4 = 0 is 4. Write value of p.
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Short Answer Type
79.Find the discriminant of the quadratic equation.
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80.Show that x = – 3 is a solution of x2 + 6x + 9 = 0.