Question 633114
Square root of the first term = 5x
Square root of the last term = 2
twice the product of 5x and 2 = 20x
Answers: {{{highlight(20x)}}} or {{{highlight(-20x)}}}

Check:
{{{(5x + 2)^2 = 25x^2 + 20x + 4}}} and
{{{(5x - 2)^2 = 25x^2 - 20x + 4}}}