B. 64x3 - 125
factor sum or difference of cubes

  (4x -5)(16x^2 +20x +25)

Step-by-step explanation:

The factoring of the difference of cubes is something you might want to memorize, or keep handy:

  (a³ -b³) = (a -b)(a² +ab +b²)

Here, the minus sign in the middle tells you this is a difference. The power of x is a clue that this might be the difference of cubes. Your knowledge of cubes of small integers tells you ...

so you can recognize this as ...

  (4x)³ - 5³ . . . . . the difference of cubes.

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Since you are familiar with the factorization above, you can easily write down the factoring of this expression using a=4x, b=5.

  (4x -5)(16x² +20x +25)

For "completeness", here is the factorization of the sum of cubes:

  a³ +b³ = (a +b)(a² -ab +b²)

Note the linear factor (a +b) has the same sign as the sign between the cubes. The sign of the middle 2nd-degree term (ab) is opposite that.

18

step-by-step explanation:

draw the shape and you will see that f and k are actually at adjacent vertices (points of the hexagon that are neighboring).   so find the distance between (1,2) and (4,2).   that is easy since (1,2) and (4,2) is just a vertical distance to count, which is 3.   it is a regular polygon which means all sides are congruent.   you have 6 sides (hexa) so multiply 6 by 3 to receive 18.