Solve for x: 4+7+10...+x= 286
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Answer:
Step-by-step explanation:
It is an AP with,
a=4 , d=3 , sn=286
sn=n/2[2a+(n-1)d]
286=n/2[2(4)+(n-1)3]
286=n/2[8+3n-3]
286*2=n[5+3n]
572=5n+3n^2
3n^2+5n-572
n=13
n=(l-a)/d+1
13=(l-4)/3+1
13=(l-4+3)/3
39=l-1
l=40
x=40
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