Question 173894
Expand through "FOIL" (first, outer, inner and last)
.
(4x + 3)(3x + 1)
First:  4x(3x) = 12x^2
Outer: 4x(1) = 4x
Inner: 3(3x) = 9x
Last: 3(1) = 3
.
Putting it all together we have:
12x^2 + 4x + 9x + 3
12x^2 + 13x + 3
.
The second expansion works the same as above.
For review of FOIL see:
http://www.mathwarehouse.com/algebra/polynomial/foil-method-binomials.php