20 POINTS (Again) Helppp Hurry!!

What is the number 321,000,000 in scientific notation? also what is the number? ?

Plz determine whether the polynomial is a difference of squares and if it is, factor it. y2 – 196 is a difference of squares: (y + 14)2 is a difference of squares: (y – 14)2 is a difference of squares: (y + 14)(y – 14) is not a difference of squares

If a 36 inch yardstick casts a 21 foot shadow, how tall is a building whose shadow is 168 feet? what is the scale factor