Let’s resolve into factors

x²y² + 23xy-420

To resolve it into factors, we first factorize 420

420= 2×2×3×5×7

Given, x² + (p + q)x + pq=(x + p)(x + q) … (2)

Comparing 1 and 2

p + q = 23

pq =-420

∴ (1) can be written as

x²y² + 35xy-12xy-420

= (xy + 35)(xy-12)

∴ The resolved factors are (xy + 35)(xy-12).