Step-by-Step Strategies for Functions and Inequalities in CAT Quant Section

Ankita Jha

Updated On: September 15, 2025 10:48 PM

The basic strategy to solve questions on Functions and Inequalities in CAT Quant Section is to first check the domain. For functions always look for symmetry form while for inequalities use the number line test. 


 
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Functions and Inequalities

In the CAT exam, usually questions from Functions and Inequalities are usually integrated with topics like quadratic equations, modulus, relations, differentiation. With respect to questions in CAT Functions and Inequalities from Quant Section it is important to start with domain analysis and thereby classify the function whether it is linear, quadratic or modulus. Moreover for the inequalities section it is important to express the inequality in the standard form and isolate the variable on the one side of the equation. In this article we have systematically highlighted on how to solve these questions correctly in the CAT exam.

Also Read: Analyzing Your CAT Mock Test

Step-by-Step Strategy for Functions

Aspirants can follow the steps to solve the questions on functions.

Steps

Details

Understand the Question

Take note that the domain of the function is the valid input while the range is the possible output

Check Domain of Function

In order to check domain restrict the value to

  • Denominators (≠ 0)
  • Square roots (≥ 0)
  • Logarithms (> 0)
  • Absolute values (case-split if needed)

Next Find Range

To find range follow the transformation method by using Quadratic, Rational and Composition techniques

Use Graphical Representation

Rough sketches help with symmetry (odd/even functions), increasing/decreasing behavior, and boundary values.

For Functions, candidates must take note that

  • Use Substitution Method for options
  • f(x+y) = f(x)+f(y) → linear function
  • Modulus Function - Split two cases

Also Read: Effective Guessing Strategies for CAT Verbal Ability

Step-by-Step Strategy for Inequalities

Aspirants can follow the steps to solve the questions on inequalities

Steps

Details

Simplify Expression

Factorise the quadratic equation. Bring the values to one side

Use Number Line Method

  • Plot critical points on a line.
  • Test sign in each interval.
  • Decide open/closed interval depending on ≥, ≤

Absolute Value

Split into cases based on sign

Exponential / Logarithmic

  • If base > 1 → inequality direction unchanged.
  • If 0 < base < 1 → inequality flips.

For Inequalities, candidates must take note that

  • Use symmetry (e.g., |x| ≥ k always gives two branches).
  • Eliminate wrong options quickly with test values.
  • For equation ax² + bx + c > 0 → solution lies outside roots if a > 0.
  • For equation ax² + bx + c < 0 → solution lies between roots if a > 0.

Also Read: Caselets vs Graphs in CAT DILR and How to Choose

Tricks to Solve Functions in CAT

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Applicants can follow the methods to solve Functions in CAT exam.

Method

Detailed Steps

Substitution Method

  • When asked to find f(f(x)) or f(g(x)) substitute step by step

Tip:

If f(x) = x2+1 then f(f(x)) = f(x2+1) = (x2+1)2+1.

Use Graph Visualization

Replace f(x)=∣g(x)∣ with cases

  • If g(x) ≥ 0 then f(x) = g(x)
  • If g(x) < 0 then f(x) = - g(x)

Piecewise Functions

For modulus or floor functions, break into intervals

Example: f(x) = ∣x−2∣

Case 1 - x ≥ 2 → f(x) = x−2

Case 2 - x < 2 → f(x) = - (x - 2) = 2 - x

Tricks to Solve Inequalities in CAT

Applicants can follow the methods to solve Functions in CAT exam.

Methods

Tricks

Tricks for Linear Inequalities

Solve like equations, but flip the inequality sign when multiplying/dividing by a negative number.

For example-

-2x > 6 ⟹ x < –3

Tricks for Quadratic Inequalities

  • Factorize the quadratic (if possible).
  • Find the critical points (roots)
  • If coefficient of x² > 0 → parabola opens upward
  • If the coefficient of x² < 0 → parabola opens downward.

Tricks for Rational Inequalities

  • Factorize numerator & denominator separately.
  • Mark critical points (where numerator = 0 or denominator = 0).
  • Draw number line → test signs of each interval.
  • Exclude points where denominator = 0.

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FAQs

What’s a step-by-step trick for solving rational inequalities (fractions)?

  • Identify where numerator = 0 and denominator = 0.
  • Mark these as critical points.
  • Test intervals between them.
  • Remember: denominator ≠ 0, so exclude those points.

How should I approach modulus-based function problems step-by-step?

  • Remove modulus by considering different cases (+ and –).
  • Solve each case separately.
  • Ensure the solution satisfies the condition of that case.
  • Combine valid solutions.

Should I always check boundary points in inequalities?

Yes. Boundary points (where the expression = 0 or undefined) determine the intervals where the inequality flips. Always test if they should be included (≤, ≥) or excluded (<, >).

What is the first step in solving function-based problems in CAT?

The first step is to understand the function’s definition and domain. Always check whether the function is polynomial, modulus-based, piecewise, or composite. This helps decide the solving strategy.

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