Question 86479
The given expression is: 


{{{(10a^2 + ab - 2b^2)}}}  ==> To factor out completely 


The product of the last term is {{{20a^2b^2}}} which cna be expressed as the 

sum of the middle term and that is given by: +5ab and - 4ab


Thus, the above expression can be written as:


{{{(10a^2 + 5ab - 4ab - 2b^2)}}} 


5a(2a + b) - 2b(2a + b) 


Taking (2a + b) as a common factor, we get: 


(2a + b)(5a - 2b) 


Hence, the solution.


Regards