JEE doubts
500 doubts found
What does “Permutation” actually mean in Permutations & Combinations, and why does it matter for JEE?
an arrangement where order matters: nPr = n!/(n−r)!.
What does “Binomial expansion” actually mean in Binomial Theorem, and why does it matter for JEE?
(a+b)^n expands as a sum of terms nCr·a^(n−r)·b^r, with coefficients from Pascal's triangle.
What does “Pythagorean identity” actually mean in Trigonometry, and why does it matter for JEE?
for any angle, sin²θ + cos²θ = 1.
What does “Slope” actually mean in Straight Lines, and why does it matter for JEE?
the steepness of a line, m = (y₂−y₁)/(x₂−x₁) = tanθ.
What does “Eccentricity” actually mean in Conic Sections, and why does it matter for JEE?
a number e that classifies conics: circle e=0, ellipse e<1, parabola e=1, hyperbola e>1.
What does “Limit” actually mean in Limits & Continuity, and why does it matter for JEE?
the value a function approaches as the input nears a point, even if it isn't defined there.
What does “Derivative” actually mean in Differentiation, and why does it matter for JEE?
the instantaneous rate of change of a function — the slope of the tangent at a point.
What does “Antiderivative” actually mean in Integration, and why does it matter for JEE?
integration reverses differentiation; an indefinite integral always carries a constant of integration +C.
What does “Basic probability” actually mean in Probability, and why does it matter for JEE?
probability = favourable outcomes ÷ total outcomes, always between 0 and 1.
What does “Dot product” actually mean in Vectors & 3D Geometry, and why does it matter for JEE?
a·b = |a||b|cosθ gives a scalar and is zero when the vectors are perpendicular.
I keep getting “Discriminant” questions wrong in Quadratic Equations. What's the trap?
thinking D<0 means 'no solution'.
I keep getting “The imaginary unit” questions wrong in Complex Numbers. What's the trap?
writing √(−1)·√(−1) = √1 = 1.
I keep getting “Arithmetic progression” questions wrong in Sequences & Series. What's the trap?
using the wrong count (n vs n−1) for the nth term.
I keep getting “Permutation” questions wrong in Permutations & Combinations. What's the trap?
using permutations when order doesn't matter.
I keep getting “Binomial expansion” questions wrong in Binomial Theorem. What's the trap?
forgetting that the powers of a and b add up to n in every term.
I keep getting “Pythagorean identity” questions wrong in Trigonometry. What's the trap?
misremembering it as sinθ + cosθ = 1.
I keep getting “Slope” questions wrong in Straight Lines. What's the trap?
inverting the formula to (x₂−x₁)/(y₂−y₁).
I keep getting “Eccentricity” questions wrong in Conic Sections. What's the trap?
mixing up which conic each eccentricity range gives.
I keep getting “Limit” questions wrong in Limits & Continuity. What's the trap?
assuming the limit always equals the function's value at that point.
I keep getting “Derivative” questions wrong in Differentiation. What's the trap?
confusing the derivative (a rate) with the function's value.
I keep getting “Antiderivative” questions wrong in Integration. What's the trap?
forgetting to add +C to an indefinite integral.
I keep getting “Basic probability” questions wrong in Probability. What's the trap?
giving a probability greater than 1.
I keep getting “Dot product” questions wrong in Vectors & 3D Geometry. What's the trap?
expecting the dot product to be a vector.
What does “Sum and product of roots” actually mean in Quadratic Equations, and why does it matter for JEE?
for ax²+bx+c=0, the roots add to −b/a and multiply to c/a (Vieta's relations).