Part (1)
9x2+6x+1−25y2
=(3x)2+2×3x×1+(1)2−(5y)2
=(3x+1)2−(5y)2∴(a2−b2=(a+b)(a−b))
=(3x+1+5y)(3x+1−5y)
Hence, this is the answer
Part (2)
a2+b2+2ab
=a2+ab+ab+b2
=a(a+b)+b(a+b)
=(a+b)(a+b)
And
2bc+2ca
=2c(b+a)
=2c(a+b)
Hence, this is the answer.