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K8B
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#1
Report Thread starter 13 years ago
#1
hey
know im being really silly but will someone please show me how I do this?!

9^a – 2 × 3^(a+1) + 8 = 0

(a= 0.631 or 1.26 apparently but no idea how)
thanks!
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RichE
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#2
Report 13 years ago
#2
(Original post by salk8)
hey
know im being really silly but will someone please show me how I do this?!

9^a – 2 × 3^(a+1) + 8 = 0

(a= 0.631 or 1.26 apparently but no idea how)
thanks!

Write y = 3^a then your equation can be rewritten as

y^2 - 6 y + 8 = 0

(y - 2)(y-4) = 0

So y = 2 or 4

and a = log_3(2) or log_3(4)
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m:)ckel
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#3
Report 13 years ago
#3
9a - 2(3a+1) + 8 = 0
32a - 2[(3a)(3)] + 8 = 0
32a - 6(3a) + 8 = 0

Using quadratic formula:

3a = [6 ± √(36-32)]/2

3a = (6±2)/2

3a = 4 or 3a = 2
aln(3) = ln(4) or aln(3) = ln(2)

a = 1.26 or a = 0.631

{Lateish...}
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K8B
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#4
Report Thread starter 13 years ago
#4
O rite thanx very much!
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