Question: how to factor quadratics using box method?
Answer: Draw a two-by-two square.
Put the first term of the trinomial in the upper-left corner and the last term in the lower-right corner.
Multiply the first and last terms: 3x2(–8) = –24x2.
Find two factors of the resulting product whose sum is the middle term, 10x. ... 
Place the factors in the two remaining squares.