Answer:
18x
Step-by-step explanation:
The HCF is the highest factor common to both expressions. We can find it by factoring both expressions and identifying common factors.
Factorization
36(x³+x²y-12xy²) = 18x·2·(x +4y)(x -3y)
54(x³y+4x³y²-21xy) = 18x·3y·(x +7)(x -3)
The highest common factor is 18x.
