Let $f(x) = 3x + 5$, for $x \in \mathbb{R}$ - Junior Cycle Mathematics - Question 4 - 2015
Question 4
Let $f(x) = 3x + 5$, for $x \in \mathbb{R}$.
(a) Find the value of $f(7)$.
(b) Write $f(k)$ in terms of $k$.
(c) Using your answer to part (b), or otherwise, find... show full transcript
Worked Solution & Example Answer:Let $f(x) = 3x + 5$, for $x \in \mathbb{R}$ - Junior Cycle Mathematics - Question 4 - 2015
Step 1
Find the value of $f(7)$.
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Answer
To find the value of f(7), substitute x with 7 in the function.
f(7)=3(7)+5=21+5=26.
Thus, f(7)=26.
Step 2
Write $f(k)$ in terms of $k$.
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Answer
We can express f(k) by substituting x with k in the function:
f(k)=3k+5.
Step 3
Using your answer to part (b), find the value of $k$ for which $f(k) = k$.
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Answer
To find the value of k for which f(k)=k, we set the equation:
3k+5=k.
Rearranging gives:
3k−k2kk=−5=−5=−25.
Thus, k=−25.
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