The graphs of second degree polynomials are known as

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Me. i can't figure out this question. give an explanation too. .

Aculture started with 4,000 bacteria. after 5 hours, it grew to 5,200 bacteria. predict how many bacteria will be present after 19 hours. round your answer to the nearest whole number.