If \(f(x)=4x-1\) and \(f(a)=19\), what is the value of \(a\)?
Substitute \(x=a\) into the function: \(f(a)=4a-1\). Since \(f(a)=19\), we have \(4a-1=19\). Adding 1 to both sides gives \(4a=20\), and dividing by 4 gives \(a=5\). Option B is incorrect because \(a=4\) would give \(f(4)=16-1=15\), not 19. Exam tip: Verify the answer by substituting it back into the original function.
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