ONE QUESTION, ONE STEP
ZX-CD89CA54432025年9月美国B卷 · 第 17 题
2025年9月美国B卷 · 原库模块 2 · Q17 原库参考解析
A certain investment account offers a special interest rate for the first 4 months the account is open followed by a lower interest rate for the remainder of the time the account is open. Bennett opened one of these accounts with an original account balance of $900 and did not make any other deposits or withdrawals. 4 months after Bennett opened the account, the balance had increased by 0.6% of the original balance. 6 months after Bennett opened the account, the balance had increased by an additional 0.1% of the balance at the end of the first 4 months. Every 2 months after the first 6 months, the balance had increased by an additional 0.1% of the balance 2 months before. Which of the following equations could represent the account balance \( B(x) \), in dollars, x months after the account was opened, where \( x\ge4 \)?
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