algebra
posted by tommy .
Please help
find the root(values of x when the expression is equal to zero)
3x^2+21x=0

algebra 
Steve
3x^2+21x = 0
3x(x+7) = 0
if the product of factors is zero, then one of the factors must be zero. So, when is any of the factors zero?
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how do i solve this find the root 3x^2 +21x=0 is the root 7