(ax+by)2+(bx−ay)2 factorise it
Given, (ax+by)²+(bx−ay)²
=a²x²+b²y²+2abxy+b²x²+a²y²−2abxy [∵(a+b)2=a2+b2+2ab,(a−b)2=a2+b2−2ab]
=a²x²+b²x²+b²y²+a²y²
=x²(a²+b²)+y²(a²+b²)
=(a²+b²)(x²+y²)
Hence, factorise of (ax+by)2+(bx−ay)2 is (a2+b2)(x2+y2)