Hello from MrBillDoesMath!
Answer:
15 x^4 z^2
Discussion:
Only x and z appear in both expressions so I am looking for the highest power of x and z in both terms. This is clearly
x^4z^2
but 30 and 75 (constant) are both divisible by 15 so the final gcf is 15 x^4 z^2
Thank you,
MrB
