Question #de4b1
1 Answer
Feb 4, 2018
Explanation:
Instead of triple-foiling and ending up with 9 terms to condense, use this trick:
The first two terms in both polynomials are the same, so you can group them together and treat them as ONE term:
#(3x+7y+1)(3x+7y-1)#
#= ((3x+7y)+1)((3x+7y)-1)#
Now, this is in the form
#(a+b)(a-b) = a^2 - b^2#
Therefore, we can write this expression as:
#= (3x+7y)^2 - 1^2#
To simplify completely, remember the square formula:
#(a+b)^2 = a^2 + 2ab + b^2#
So, we can expand the expression like this:
#((3x)^2 + 2(3x)(7y) + (7y)^2) - 1#
#(9x^2 + 42xy + 49y^2) - 1#
#9x^2 + 42xy + 49y^2 - 1#
Final Answer