a + a*r + a*r^2 = 7a (1) (a is the first term)
a + a*r + a*r^2 + a*r^3 = 45 (2)
Divide each term in (1) by a:
1 + r + r^2 = 7 or r^2 +r - 6 = 0 or (r -2)(r + 3) = 0 r = 2 or r = -3
Factor a from (2) and rearrange as:
a = 45/(1 + r + r^2 + r^3)
a = 45/(7 + r^3)
If r = 2 then a = 45/15 or a = 3
If r = -3 then a = 45/(7 - 27) or a = -45/20 or a = -9/4
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