Recall the (15,7)-block BCH code in Example 22.2.6. By Theorem 8.1.13, this code is capable of correcting two errors. Suppose that these errors occur in bits a1 and a2. The error-locator polynomial is s(x)=(x+ωa1)(x+ωa2). Show that
s(x)=x2+s1x+(s12+s1s3).