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1920 Paper 3 Q212
D: 1500.0 B: 1500.0

Find the maximum and minimum values of \[ (x+3)^2(x-2)^3, \] and draw a rough graph of the function. Hence, or otherwise, prove that the equation \[ x^5 - 15x^3 + 10x + 60 = 0 \] has two real negative roots and two imaginary roots.

1920 Paper 3 Q213
D: 1500.0 B: 1500.0

Integrate

  1. [(i)] \(\int \frac{dx}{\sin x + \cos x}\),
  2. [(ii)] \(\int \frac{dx}{(x-1)^2(x+1)}\),
  3. [(iii)] \(\int_1^2 \sqrt{\{(x-1)(2-x)\}} \, dx\).

1920 Paper 3 Q214
D: 1500.0 B: 1500.0

Find the area of the loop of the curve \[ a^3y^2 = x^4(2x+a). \]

1920 Paper 3 Q301
D: 1500.0 B: 1500.0

\(ABC\) is a triangle inscribed in a circle. \(AP\) is a chord of the circle which bisects \(BC\), and the tangent at \(P\) meets \(BC\) in \(N\). Prove that \[ NC:NB = AB^2:AC^2. \]

1920 Paper 3 Q302
D: 1500.0 B: 1500.0

\(OP, OQ\) are tangents at \(P, Q\) to a parabola, and the line bisecting \(PQ\) at right angles meets the axis in \(G\). Prove that the focal chord parallel to \(PQ\) bisects \(OG\).

1920 Paper 3 Q303
D: 1500.0 B: 1500.0

Shew that it is possible for two perpendicular normal chords of an ellipse to meet on the curve if \(e^2 \ge \frac{2}{3}\). Shew also that in this case each of the chords is trisected by another perpendicular normal chord.

1920 Paper 3 Q304
D: 1500.0 B: 1500.0

\(OBP, OAQ\) are the asymptotes of a conic, \(A, B\) being fixed points and \(PQ\) a variable tangent. Prove that \(PA, QB\) will intersect on a conic which has parallel asymptotes and passes through \(A, B\).

1920 Paper 3 Q305
D: 1500.0 B: 1500.0

Prove that the foci of the hyperbola \(xy - 2ax - 2by + 2a^2 = 0\) lie on one or other of the parabolas \(y^2 = 4ax, y^2 = 4a(2a-x)\).

1920 Paper 3 Q306
D: 1500.0 B: 1500.0

Shew that, if \(a, b, c, x, y, z\) denote real numbers, and the sum of any two of the three \(a, b, c\) is greater than the third, then \[ a^2(x-y)(x-z) + b^2(y-x)(y-z) + c^2(z-x)(z-y) \] is positive.

1920 Paper 3 Q307
D: 1500.0 B: 1500.0

Prove that, if \(N\) and \(n\) are nearly equal, then \[ \left(\frac{N}{n}\right)^{1/3} = \frac{N+n}{n + \frac{1}{3}\frac{N+n}{4n-N}} \text{ approximately,} \] the error being approximately \(\frac{7}{81}\left(\frac{N-n}{n}\right)^3\).