From ee78c07528222f920785acf7bef8deec92cf815a Mon Sep 17 00:00:00 2001
From: "18218461270@163.com" <18218461270@163.com>
Date: Thu, 31 Jul 2025 21:45:44 +0800
Subject: [PATCH] update chapter2 homework

---
 homework/chapter2/README.md | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/homework/chapter2/README.md b/homework/chapter2/README.md
index 0142980..62132d7 100644
--- a/homework/chapter2/README.md
+++ b/homework/chapter2/README.md
@@ -28,7 +28,12 @@ b&=(a+x_{w-1}\cdot y+y_{w-1}\cdot x)\bmod 2^w\\
 \end{aligned}$$
 
 ## 2.80
-先得到粗糙的结果 `(x >> 2) + ((x >> 2) << 1)`，再根据 `x & 3` 以及 $x$ 的符号（决定舍入方向）进行修正。
+$$
+\texttt{threefourths(x)}=\left\{\begin{aligned}
+&3\cdot\lfloor x/4\rfloor+x\bmod 3-[x\bmod 3\neq0], &x\ge0\\
+&3\cdot\lfloor x/4\rfloor+x\bmod 3, &x<0
+\end{aligned}\right.
+$$
 
 ## 2.97
-在某些情况下，舍入会导致最高位变化。对于这种情况，我们要将最低有效位提高一位。
\ No newline at end of file
+在某些情况下，舍入会导致最高位提高一位。对于这种情况，我们要将舍入时的最低有效位相应提高一位。
\ No newline at end of file