Question 1076094
If {{{ (a-b)^2= 289 }}} and {{{ (a+b)^2= 169 }}}, then what is the value of |4ab| ?
<pre>{{{(a - b)^2 = 289}}}______{{{a^2 - 2ab + b^2 = 289}}} ------- eq (i)
{{{(a + b)^2 = 169}}}______{{{a^2 + 2ab + b^2 = 169}}} ------- eq (ii) 
4ab = - 120 -------- Subtracting eq (i) from eq (ii)
{{{highlight_green(matrix(1,5, abs(4ab), "=", abs(- 120), "=", 120))}}}
That’s all. No need to do all types of calculations to get to the answer.
Certainly no need to find a, then b, then 4ab. That's not necessary, at all!