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First factor the each term in the expression.
\42x3y = 2 · 3 · 7 · x · x · x · y
\70xy2 = 2 · 5 · 7 · x · y · y
\The GCF is the product of the common prime factors in each term.
\GCF = 2 · 7 · x · y = 14xy ![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
The greatest common factor of 42x3y and 70xy2 is 14xy.