How do you find #f(n-1)# if #f(x)=2x^2-x+9#? Precalculus Functions Defined and Notation Function Composition 1 Answer Shwetank Mauria Oct 20, 2017 We just subsitute #x# with #n-1# and carrying out all algebraic operations we get #f(n-1)=2n^2-5n+12# Explanation: We just subsitute #x# with #n-1# and carry out all algebraic operations. As #f(x)=2x^2-x+9# #f(n-1)=2(n-1)^2-(n-1)+9# = #2(n^2-2n+1)-n+1+9# = #2n^2-4n+2-n+1+9# = #2n^2-5n+12# Answer link Related questions What is function composition? What are some examples of function composition? What are some common mistakes students make with function composition? Is function composition associative? Is it always true that #(f@g)(x) = (g@f)(x)#? If #f(x) = x + 3# and #g(x) = 2x - 7#, what is #(f@g)(x)#? If #f(x) = x^2# and #g(x) = x + 2#, what is #(f@g)(x)#? If #f(x) = x^2# and #g(x) = x + 2#, what is #(g@f)(x)#? What is the domain of #(f@g)(x)#? What is the domain of the composite function #(g@f)(x)#? See all questions in Function Composition Impact of this question 2703 views around the world You can reuse this answer Creative Commons License