There are some binomials that can be expanded directly by a general inspection. For example (x+a)(x+b)=x^2+x(a+b)+ab.

Can you recognize to which case the following expression belongs?

(3x+7)(7x-3)

Question

There are some binomials that can be expanded directly by a general inspection. For example (x+a)(x+b)=x^2+x(a+b)+ab.

Can you recognize to which case the following expression belongs?

(3x+7)(7x-3)

anonymous · Answer

$$3\times7 \times(x+(7/3))\times(x-(3/7))$$if you really wanted to , then you could express it as :$$( 3 (x+(7/3) ) (7 (x-(3/7) ) )$$

and then use the formula
then take out the constant factors to get

anonymous · Answer

lol the first line of the last post be under the third line , if you get what I mean lols.

Nevertheless, it is much easier to just expand it as a binomial straight away

ie get 21x^2 -9x +49x -21 , and collect terms

anonymous · Answer

Are you using the foiling method? There are some binomial that can be multiplied and the answer can be found at a first glance. Like the example I gave you at the first line.

anonymous · Answer

Can you recognize what case does this example belongs to? According with wikipedia, there is not such a case. But we end up with a ax^2+bx+c expression.