Prove that (a-b) x (a+b)=2a x b is true. (a and b are vectors)

It takes evan 6 3/4 to mow 3 lawns. it takes 2 1/3 hours to mow me. gals lawn and 1 3/4 hot mow ms. lee’s lawn. how many hours does it take evan to mow the third lawn?

Iwant to know what 3g+5h+4g-2h is my teacher is too selfish to tell us

The size of a certain cell is 2.5*10^-9m. another cell is 1.5*10^3 times larger. how large is the larger cell in scientific notation?