Sum of three consecutive term of an arithmetic progression is 42 and their product is 2520. Find the term of arithmetic progression
Answers
Answer :
10 , 14 , 18 or 18 , 14 , 10 are terms of the Arithmetic Progression if Sum of three consecutive terms of an Arithmetic Progression is 42 and their product is 2520.
Step-by-step explanation:
Let say three terms of an AP are
a - d , a , a + d
Sum = a - d + a + a + d = 3a
3a = 42
=> a = 14
(a - d)a (a + d) = 2520
=> (14 - d)14(14 + d) = 2520
=> 196 - d² = 180
=> d² = 16
=> d = ± 4
Three terms are 10 , 14 , 18 or 18 , 14 , 10
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GIVEN :
Sum of three consecutive terms in an Arithmetic Progression = 42
Their product = 2520
Let the terms be (a - d), a and (a + d)
(a - d) + a + a + d = 42
a - d + a + a + d = 42
=> 3a = 42
=> a = 42/3
=> a = 14
(a - d) × a × (a + d)
(a - d) × 14 × (a + d) = 2520
(a - d) (a + d) = 2520/14
a² - d² = 180 [ (a - b) (a + b) = a² - b² ]
(14)² - d² = 180
196 - 180 = d²
=> d² = 16
=> d = √16
=> d = ±4
TERMS :
If d = -4,
First term = a - d = 14 - (-4) = 18
Second term = a = 14
Third term = a + d = 14 + (-4) = 10
If d = 4,
First term = a - d = 14 - 4 = 10
Second term = a = 14
Third term = a + d = 14 + 4 = 18
Therefore, the terms are 18, 14 and 10 or 10, 14 and 18.
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