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Question 1371
StructuredStandard5 marks
CBSE Class 11 Mathematics · Limits and Derivatives · Derivatives from first principles

For f(x)=x¹⁰⁰/100+x⁹⁹/99+⋯+x²/2+x+1, prove f′(1)=100f′(0).

Question 1372
StructuredStandard5 marks
CBSE Class 11 Mathematics · Straight Lines · Distance and intersections

Find the line perpendicular to x−7y+5=0 whose x-intercept is 3.

Question 1373
StructuredStandard5 marks
CBSE Class 11 Mathematics · Sequences and Series · Geometric progressions

A geometric progression has first term a, nth term b and product P of all n terms. Prove P²=(ab)ⁿ.

Question 1374
StructuredStandard4 marks
CBSE Class 11 Mathematics · Permutations and Combinations · Combinations

From 5 vowels and 21 consonants, count four-letter arrangements containing two distinct vowels and two distinct consonants.

Question 1375
StructuredStandard4 marks
CBSE Class 11 Mathematics · Trigonometric Functions · Compound-angle identities

Prove \(\cos(\frac{3\pi}{2}+x)\cos(2\pi+x)[\cot(\frac{3\pi}{2}-x)+\cot(2\pi+x)]=1\).

Question 1376
StructuredStandard2 marks
CBSE Class 11 Chemistry · Organic Chemistry: Some Basic Principles and Techniques · Purification and qualitative analysis

Identify the Prussian-blue compound responsible for a positive Lassaigne nitrogen test.

Question 1377
StructuredStandard3 marks
CBSE Class 11 Chemistry · Equilibrium · Acid-base equilibria and pH

What will be the conjugate bases for the Brönsted acids:

(a)
HF
(b)
H2SO4
(c)
HCO–3?
Question 1378
StructuredStandard3 marks
CBSE Class 11 Chemistry · Chemical Bonding and Molecular Structure · Valence-bond and molecular-orbital theories

What do plus and minus signs on orbital lobes signify?

Question 1379
McqStandard2 marks
CBSE Class 11 Chemistry · Classification of Elements and Periodicity in Properties · Ionisation and electron-gain enthalpy

Which statement about ionisation enthalpy is incorrect?

Question 1380
StructuredStandard3 marks
CBSE Class 11 Chemistry · Structure of Atom · Subatomic particles and atomic symbols

The diameter of a zinc atom is 2.6 Å. Calculate (a) its radius in pm(b) the number of atoms that fit side by side in \(1.6\,\mathrm{cm}\).