Question

find the greatest common monomial factor of the terms :
49x^4y^2, 7x^9 y^6, 28x^7

Answer 1

First, decompose every number in its prime factors. You have
$49 = {7}^{2}$
$28 = {2}^{2} \cdot7$
Then for each number and each letter present in each monomial, you take the smallest power appearing. It gives you
$7 {x}^{4}$