Let the function f be defined as f(x)=5x^2-7(4x+3). What is the value of f(3)?

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This is a practice ACT question and it has me stumped. I know the answer is -60 but I do not know what the question is asking nor how to solve.

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Answer 1 · 2017-06-04T08:00:40

#f(3)=-60#

If we have #f(x)# to calculate #f(3)#, we just replace #x# with #3#, the value which is taken by #x# and you have #f(3)#.

Here you have #f(x)=5x^2-7(4x+3)#

so #f(3)=5xx3^2-7(4xx3+3)#

#=5xx9-7(12+3)#

#=45-7xx15#

#=45-105#

#=-60#