Question

The 6^th term of an A.P. = 2, the value of common different of an A.P. which makes the product a₁.a₄.a₆ least is –

• A. d = 8/5
• B. d = 5/4
• C. d = 2/3
• D. None of these

Answer 1

Answer: (D)

None of these

Answer 2

y = a₁.a₂.a₆ a + 5d = 2

y = 2a.(a + 3d) a = 2 – 5d

y = 2(2 – 5d) (2 – 5d + 3d)

y = 2(5d – 2) (2d – 2) d₁= $\frac { 2 } { 5 }$ d₂=1

Y_(min) at d = $\frac { \mathrm { d } _ { 1 } + \mathrm { d } _ { 2 } } { 2 }$ = $\frac { \frac { 2 } { 5 } + 1 } { 2 }$ = $\frac { 7 } { 10 }$