The equation of a polynomial is given by .
- (i)
Find the remainder when is divided by .
- (ii)
Show that the equation has only one real root.
- (iii)
Hence, solve the equation .
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Worked solution
9(i)
1. Apply the Remainder Theorem by substituting $x = \frac{1}{2}$ into $\mathrm{p}(x)$
Remainder
2. Evaluate the expression to find the remainder
9(ii)
1. Find a linear factor of $\mathrm{p}(x)$ using the Factor Theorem
Let .
By trial and error,
.
Therefore, is a factor of .
2. Factorise the polynomial completely into a linear and a quadratic factor
By comparing coefficients:
Comparing coefficients of :
So, .
3. Evaluate the discriminant of the quadratic factor
For the quadratic equation ,
Discriminant,
4. Conclude the number of real roots
Since , the quadratic equation has no real roots.
Thus, is the only real root of .
Shown that is the only real root.
9(iii)
1. Rewrite the exponential equation to reveal the polynomial structure
2. Use the substitution $x = 2^y$ and the result from part (ii)
Let . The equation becomes:
This is . From part (ii), the only real root is .
3. Solve for $y$
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