Question

how many terms of the AP 45,39,33..... must be taken so that their sum is 180
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Answer 1

Answer

Sn = 180

n/2 [90 + (n - 1)(-6)] = 180

90n – 6n2 + 6n = 360

⇒ 6n2 – 96n + 360 = 0

⇒ 6[(n – 6)(n – 10)] = 0

⇒ n = 6, n = 10

Sum of a7, a8, a9, a10 = 0

∴ n = 6 or n = 10

Answer 2

Answer:

given in a.p

a =45

d = -6

an = 180

n =?

Step-by-step explanation:

according to A.p's formula

45+(n-1)×-6 = 180

45- 6n + 6 = 180

question wrong hai n kabhi negative nahi ho sakta...