Suppose you have a product a*b*c = 0a⋅b⋅c=0. Then if any of a, ba,b or cc is equal to zero, the equation is true. This is because any number times zero is equal to zero. For example, if you have a = 0a=0, then 0*b*c = 00⋅b⋅c=0, which is true. This is true for any number of terms in the product.
In your case, you have two terms in your product, (3k)*(k+10) = 0(3k)⋅(k+10)=0. As per above, the equation is true when any of the terms are zero. We solve for this algebraically by setting each one to zero.
3k = 0 -> k = 03k=0→k=0
k + 10 = 0 -> k = -10k+10=0→k=−10
These are the solutions to the problem.
