Find $x$ if
\[1 + 5x + 9x^2 + 13x^3 + \dotsb = 85.\]
Question:
Find $x$ if
\[1 + 5x + 9x^2 + 13x^3 + \dotsb = 85.\]
Answer:
Let's think step by step.

user
\frac{4}{5}
Find $x$ if
\[1 + 5x + 9x^2 + 13x^3 + \dotsb = 85.\]
train