Me with these questions , i don’t understand scientific notation!

G(x)=x2-16xb=-16, so =16 = 649(x) = (x2 - 16x + 64) - 649(x) = (x - 1)2-

What is the standard deviation of the following data set rounded to the nearest tenth? 3, 17, 18, 15, 12, 21, 9

Pick the expression that matches this description: a polynomial of the 5th degree with a leading coefficient of 7 and a constant term of 6 (choice a) 7x^5+2x^2+6 (choice b) 7x^6−6x^4+5 (choice c) 6x^7−x^5+5 (choice d) 6x^5+x^4+7