这是因为在上面的例子中，a（a++）增加了两倍。另外，您还混淆了a和i。正确的一个是：

int a = 2;
int b = 5;
for (int i = a; i <= b; i++)
{
    printf("%d * %d = %d\n", a, i, a * i);
}

它打印：
2 * 2 = 4
2 * 3 = 6
2 * 4 = 8
2 * 5 = 10

int main() {
int a = 2;
int b = 6;
int result = 1;  // Initialize the result variable to 1 for multiplication

// Perform multiplication from a to b
for (int i = a; i <= b; i++) {
    result *= i;
}

printf("The multiplication result from %d to %d is: %d\n", a, b, result);

return 0;

}