Question 70542
Find a value for k so that 9m^2- kn^2 will have the factors 3m + 7n and 3mn -7n.

The difference of perfect squares factor like this:
{{{highlight(a^2-b^2=(a+b)(a-b))}}}
b^2=b*b
so:
{{{kn^2=7n*7n}}}
{{{kn^2=49n^2}}}
{{{highlight(k=49)}}}
Happy Calculating!!!!