3+5+7 ......+n terms /5+8+11+.....10terms =7 find n
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Answered by
10
3+5+7........+ n terms
a = 3
d = 2
n = n
Sn = n[2a+(n-1)d]/2
Sn = n[2(3)+(n-1)2]/2
Sn = n[6+2n-2]/2
Sn = n[4+2n/2
Sn = n ×2[2+n]/2
Sn = n(2+n)
5+8+11......... 10 terms
a = 5
d = 3
n = 10
S10 = ?
Sn = n[2a+(n-1)d]/2
S10 = 10[2(5)+(9)3]
S10 = 5[10+27]
S10= 5(37)
S10 = 185
SO
3+5+7......+n terms/5+8+11+......10terms = 7
n(2+n)/185 = 7
n²+2n/185 = 7
(cross multiplication)
n²+2n = 185×7
n²+2n = 1295
n²+2n-1295 = 0
n²+37n-35n-1295 = 0
n(n+37)-35(n+37) = 0
(n+37) (n-35) = 0
n = -37. n = 35
so the n value always be positive
so the n = 35
a = 3
d = 2
n = n
Sn = n[2a+(n-1)d]/2
Sn = n[2(3)+(n-1)2]/2
Sn = n[6+2n-2]/2
Sn = n[4+2n/2
Sn = n ×2[2+n]/2
Sn = n(2+n)
5+8+11......... 10 terms
a = 5
d = 3
n = 10
S10 = ?
Sn = n[2a+(n-1)d]/2
S10 = 10[2(5)+(9)3]
S10 = 5[10+27]
S10= 5(37)
S10 = 185
SO
3+5+7......+n terms/5+8+11+......10terms = 7
n(2+n)/185 = 7
n²+2n/185 = 7
(cross multiplication)
n²+2n = 185×7
n²+2n = 1295
n²+2n-1295 = 0
n²+37n-35n-1295 = 0
n(n+37)-35(n+37) = 0
(n+37) (n-35) = 0
n = -37. n = 35
so the n value always be positive
so the n = 35
Answered by
0
Answer:
35
Step-by-step explanation:
by solving n^2+2n-1295
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