X2-8x+21 make the expression (x-h)2+k is equivalent

X2-8x+21 = x² - 8x + (8/2)²- (8/2)² + 21

= (x² - 8x + 16 ) - 16 + 21
= (x - 4)²+ 5

This is what i found “an explicit formula designates the nth term of the sequence, as an expression of n (where n = the term's location). it defines the sequence as a formula in terms of n. this example is an arithmetic sequence(the same number, 5, is added to each term to get to the next term).” i hope this you for what your looking for. can you plz mark me brainliest?