Question:
If the sum of n terms of an A.P. is given by Sn = 3n + 2n 2, then the common difference of the A.P. is
(A) 3
(B) 2
(C) 6
(D) 4
Solution:
(D) 4
Explanation:
To find: Common Difference of A.P that is d
Consider,
Sn = 3n + 2n2
Putting n = 1, we get
S1 = 3(1) + 2(1)2
= 3 + 2
S1 = 5
Putting n = 2, we get
S2 = 3(2) + 2(2)2
= 6 + 2(4)
= 6 + 8
S2 = 14
Now, we know that,
S1 = a1
⇒ a1 = 5
And a2 = S2 – S1
= 14 – 5
= 9
∴ Common Difference, d = a2 – a1
= 9 – 5
= 4
Hence, the correct option is (D)
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- JEE Main
- Exam Pattern
- Previous Year Papers
- PYQ Chapterwise
- Physics
- Kinematics 1D
- Kinemetics 2D
- Friction
- Work, Power, Energy
- Centre of Mass and Collision
- Rotational Dynamics
- Gravitation
- Calorimetry
- Elasticity
- Thermal Expansion
- Heat Transfer
- Kinetic Theory of Gases
- Thermodynamics
- Simple Harmonic Motion
- Wave on String
- Sound waves
- Fluid Mechanics
- Electrostatics
- Current Electricity
- Capacitor
- Magnetism and Matter
- Electromagnetic Induction
- Atomic Structure
- Dual Nature of Matter
- Nuclear Physics
- Radioactivity
- Semiconductors
- Communication System
- Error in Measurement & instruments
- Alternating Current
- Electromagnetic Waves
- Wave Optics
- X-Rays
- All Subjects
- Physics
- Motion in a Plane
- Law of Motion
- Work, Energy and Power
- Systems of Particles and Rotational Motion
- Gravitation
- Mechanical Properties of Solids
- Mechanical Properties of Fluids
- Thermal Properties of matter
- Thermodynamics
- Kinetic Theory
- Oscillations
- Waves
- Electric Charge and Fields
- Electrostatic Potential and Capacitance
- Current Electricity
- Thermoelectric Effects of Electric Current
- Heating Effects of Electric Current
- Moving Charges and Magnetism
- Magnetism and Matter
- Electromagnetic Induction
- Alternating Current
- Electromagnetic Wave
- Ray Optics and Optical Instruments
- Wave Optics
- Dual Nature of Radiation and Matter
- Atoms
- Nuclei
- Semiconductor Electronics: Materials, Devices and Simple Circuits.
- Chemical Effects of Electric Current,
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