What must be done to the wires used to make an electromagnet before they connect A. The terminals of the battery must be coated with an insulating material
B. The wires must be rubbed with sandpaper to make their surfaces rough
C. The ends must be marked to show which end to attach to each terminal of the battery
D. The insulation must be removed from the ends of the wires

Step-by-step explanation:

To create a simple electromagnet, you'll need a source of electricity, a conductor, and metal. Wrap insulated copper wire tightly around an iron screw or nail before connecting the wire to a battery, and watch as your new electromagnet picks up small metal objects.

addition

step-by-step explanation:

hello from mrbilldoesmath!

answer:   (7x + 6y) ( 49x^2 - 42xy + 36y^2)

discussion:

in general, the factorization of a^3 + b^3 is

a^3 + b^ 3 = (a + b) ( a^2 - ab + b^2)

in our case note that 343 = 7^3 and 216 = 6^3 so the equation becomes:

343x^3 + 216y^3 = (7x)^3 + (6y)^3

if you think of a (above) as 7x and b as 6y the factorization becomes

343x^3 + 216y^3 =

((7x + 6y) (   (7x)^2 - 7x*6y + (6y)^2)   =

(7x + 6y) ( 49x^2 - 42xy + 36y^2)

you,

mrb

(a + b) (a^2 - a b + b^2)