The function f is defined by \(\mathrm{f(x) = 4x - 3}\). What is the value of \(\mathrm{f(10)}\)?
GMAT Algebra : (Alg) Questions
The function f is defined by \(\mathrm{f(x) = 4x - 3}\). What is the value of \(\mathrm{f(10)}\)?
-30
37
40
43
1. TRANSLATE the question
- The problem asks for "the value of f(10)"
- This means: substitute \(\mathrm{x = 10}\) into the function \(\mathrm{f(x) = 4x - 3}\)
2. TRANSLATE the substitution process
- Replace every x in the function with 10
- \(\mathrm{f(10) = 4(10) - 3}\)
3. Calculate the result
- \(\mathrm{f(10) = 4(10) - 3}\)
- \(\mathrm{f(10) = 40 - 3}\)
- \(\mathrm{f(10) = 37}\)
Answer: B. 37
Why Students Usually Falter on This Problem
Most Common Error Path:
Weak TRANSLATE skill: Students misread or forget part of the function
Many students see \(\mathrm{f(x) = 4x - 3}\) but only use \(\mathrm{f(x) = 4x}\) in their calculations, forgetting the "-3" completely. They calculate \(\mathrm{f(10) = 4(10) = 40}\).
This leads them to select Choice C (40).
Second Most Common Error:
Poor TRANSLATE reasoning: Students flip the sign on the constant term
Some students remember there's a 3 in the function but incorrectly use +3 instead of -3, calculating \(\mathrm{f(10) = 4(10) + 3 = 43}\).
This causes them to select Choice D (43).
The Bottom Line:
Function evaluation problems are deceptively simple - the real challenge lies in accurately reading and preserving every part of the given function during substitution.
-30
37
40
43