How many terms of A.p 9,17,,25 ..... Must be taken to give a sum of 450 ?
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number of terms =10 . this can help you
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given:
a=9
d=17-9
d=8
Sn=450
Sol:
Sn=n/2[2a+(n-1)d]
450×2=n[2(9)+(n-1)8]
900=n[18+8n-8]
900=n[10+8n]
900=10n+8n²
8n²+10n-900=0
by splitting middle term
8n²-80n+90n-900=0
8n[n-10]+90[n-10]=0
[8n+90]=0 or [n-10]=0
n=-90/80 or n=10
no. of terms cant be in -ve so n =10
pl mark it as brainliest
a=9
d=17-9
d=8
Sn=450
Sol:
Sn=n/2[2a+(n-1)d]
450×2=n[2(9)+(n-1)8]
900=n[18+8n-8]
900=n[10+8n]
900=10n+8n²
8n²+10n-900=0
by splitting middle term
8n²-80n+90n-900=0
8n[n-10]+90[n-10]=0
[8n+90]=0 or [n-10]=0
n=-90/80 or n=10
no. of terms cant be in -ve so n =10
pl mark it as brainliest
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