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Most Important Function Questions For CAT 2025 with Solutions

REEYA SINGH

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Oct 06, 2025

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Most Important Function Questions For CAT 2025 with Solutions

Function Questions For CAT  2025

Function questions are a frequent topic in the CAT Quant section. They test your understanding of how functions work, domains, ranges, composite functions, inverses, and transformations. In CAT 2025, you can expect both straightforward and tricky function problems. Below are some of the most important types of function questions you should practise to become comfortable with them.

Important Formulas for CAT Function Questions

To solve function questions easily in CAT, you should remember the key formulas and rules related to functions. These formulas help you work with domains, ranges, composite functions, inverses, and transformations quickly. They save time, reduce mistakes, and make even tricky function problems easier to handle. With regular practice, you’ll improve both your speed and accuracy in this topic.

Download CAT Functions Formula PDF

ConceptFormula / RuleExplanation / Use
Basic Functionf(x)=ax+bf(x) = ax + bf(x)=ax+bLinear function; straight-line graph
Quadratic Functionf(x)=ax2+bx+cf(x) = ax^2 + bx + cf(x)=ax2+bx+cParabola; vertex at x=−b2ax = -\frac{b}{2a}x=−2ab​
Cubic Functionf(x)=ax3+bx2+cx+df(x) = ax^3 + bx^2 + cx + df(x)=ax3+bx2+cx+dS-shaped curve
Rational Functionf(x)=ax+bcx+df(x) = \frac{ax + b}{cx + d}f(x)=cx+dax+b​May have vertical/horizontal asymptotes
Composite Functionf(g(x))f(g(x))f(g(x))Solve inner function first, then apply outer
Inverse Functionf(f−1(x))=xf(f^{-1}(x)) = xf(f−1(x))=x and f−1(f(x))=xf^{-1}(f(x)) = xf−1(f(x))=xInverse undoes the original function
Domain RuleDenominators ≠ 0, expressions under square root ≥ 0Helps find valid inputs
Range RuleFind outputs possible from domain valuesOften requires inverse or graph
Even Functionf(−x)=f(x)f(-x) = f(x)f(−x)=f(x)Symmetric about y-axis
Odd Functionf(−x)=−f(x)f(-x) = -f(x)f(−x)=−f(x)Symmetric about origin
Transformations – Horizontal Shiftf(x+c)f(x + c)f(x+c)Shifts graph left by ccc units
Transformations – Vertical Shiftf(x)+cf(x) + cf(x)+cShifts graph up by ccc units
Transformations – Stretch/Shrinkf(cx),cf(x)f(cx), cf(x)f(cx),cf(x)Stretch/shrink horizontally or vertically
Piecewise FunctionDifferent rules for different intervalsMust evaluate based on input value
Absolute Value Function( f(x) =x
Greatest Integer Functionf(x)=⌊x⌋f(x) = \lfloor x \rfloorf(x)=⌊x⌋Rounds down to nearest integer
Signum Functionf(x)={1x>00x=0−1x<0f(x) = \begin{cases} 1 & x > 0 \\ 0 & x = 0 \\ -1 & x < 0 \end{cases}f(x)=⎩⎨⎧​10−1​x>0x=0x<0​Indicates sign of input

Common Mistakes to Avoid in CAT Function Questions

While solving function problems, students often make avoidable mistakes. Here are some common ones to watch for:

  • Assuming the type wrongly: A function may look linear but has hidden domain restrictions.

  • Mixing up domain & range: Always check valid xxx values first before jumping to outputs.

  • Neglecting composite order: In f(g(x))f(g(x))f(g(x)), you must compute g(x)g(x)g(x) first, then apply fff.

  • Wrong inverse operations: Mistakes in algebra when finding f−1(x)f^{-1}(x)f−1(x) are frequent.

  • Overlooking piecewise parts: If a function is defined piecewise, ensure you're using the correct piece for the input.

  • Ignoring transformation impact: For f(x+c)f(x + c)f(x+c) or f(cx)f(cx)f(cx), wrong shifts or stretches often lead to errors.

List of CAT Function Questions

Question 1

Let $$f(x) = ax^2 + bx + c$$, where a, b and c are certain constants and $$a \neq 0$$ ?

It is known that $$f(5) = - 3f(2)$$. and that 3 is a root of $$f(x) = 0$$.

What is the other root of f(x) = 0?


Question 2

The area of the region satisfying the inequalities $$\mid x\mid-y\leq1,y\geq0$$ and $$y\leq1$$ is


Question 3

Let g(x) be a function such that g(x+1) + g(x-1) = g(x) for every real x. Then for what value of p is the relation g(x+p) = g(x) necessarily true for every real x?


Instruction for set :

DIRECTIONS for the following questions: These questions are based on the situation given below: In each of the questions a pair of graphs F(x) and F1(x) is given. These are composed of straight-line segments, shown as solid lines, in the domain $$x\epsilon (-2, 2)$$.

choose the answer as

a. If F1(x) = - F(x)

b. if F1(x) = F(- x)

c. if F1(x) = - F(- x)

d. if none of the above is true

Question 4

Show Answer Explanation

Question 5

Suppose for any real number x, [x] denotes the greatest integer less than or equal to x. Let L(x, y) = [x] + [y] + [x + y] and R(x, y) = [2x] + [2y]. Then it is impossible to find any two positive real numbers x and y for which

Show Answer Explanation

Question 6

Let $$f(x) = ax^2 + bx + c$$, where a, b and c are certain constants and $$a \neq 0$$ ?

It is known that f(5) = - 3f(2). and that 3 is a root of f(x) = 0.

What is the value of a + b + c?

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