We can change the sign of the second term, so that the two parenthesis are the same:

Now, both terms have in common a 3, becase the numeric factors are 3 and 6. If we factor the 3, we have

The parenthesis (a-1) is also in common, so we can factor it as well:

Finally, both terms in the parenthesis contain
, because it's the power of b with the lowest exponent:

So, the factorization is

You can swap the order of the four factors (3, b^2, a-1 and 2b-1) as you like: the multiplication is commutative.
Yes it’s an improper fraction because the numerator is larger than the denominator. If it was a mixed number of 1 11/15, it would not be an improper fraction.
Answer:
27.2mm²
Step-by-step explanation:
Area of a triangle =
* base * height
Base of this triangle = 8mm
Height = 6.8mm
Area = 
= 4mm * 6.8mm
= 27.2mm²
-- To create an even number:
2n is always even, no matter what 'n' is.
-- To test a number and see whether it's even:
'n' is even if (n/2) = (the greatest integer in n/2)