Exam-Style Problems

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Problem 707
707

\(The function f is defined by f(x) = -3x2 + 2 for x โ‰ค -1.\)

\(The function g is defined by g(x) = -x2 - 1 for x โ‰ค -1.\)

\(Solve the equation fg(x) - gf(x) + 8 = 0.\)

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Nov 2022 p12 q9
708

Functions f and g are defined by

\(f(x) = x + \frac{1}{x}\) for \(x > 0\),

\(g(x) = ax + 1\) for \(x \in \mathbb{R}\),

where \(a\) is a constant.

(a) Find an expression for \(gf(x)\).

(b) Given that \(gf(2) = 11\), find the value of \(a\).

(c) Given that the graph of \(y = f(x)\) has a minimum point when \(x = 1\), explain whether or not \(f\) has an inverse.

It is given instead that \(a = 5\).

(d) Find and simplify an expression for \(g^{-1}f(x)\).

(e) Explain why the composite function \(fg\) cannot be formed.

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June 2022 p13 q6
709

The function f is defined by \(f(x) = 2x^2 - 16x + 23\) for \(x < 3\).

The function g is defined by \(g(x) = 2x + 4\) for \(x < -1\).

Find and simplify an expression for \(fg(x)\).

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June 2022 p12 q10
710

Functions f and g are defined as follows:

\(f(x) = \frac{2x+1}{2x-1}\) for \(x \neq \frac{1}{2}\),

\(g(x) = x^2 + 4\) for \(x \in \mathbb{R}\).

(a) The diagram shows part of the graph of \(y = f(x)\). State the domain of \(f^{-1}\).

(b) Find an expression for \(f^{-1}(x)\).

(c) Find \(gf^{-1}(3)\).

(d) Explain why \(g^{-1}(x)\) cannot be found.

(e) Show that \(1 + \frac{2}{2x-1}\) can be expressed as \(\frac{2x+1}{2x-1}\). Hence find the area of the triangle enclosed by the tangent to the curve \(y = f(x)\) at the point where \(x = 1\) and the x- and y-axes.

problem image 710
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