In the expression 9-12 what does the negative exponent mean

What is the missing constant term in the perfect square that starts with x^2 -20x

Hi my sisters and brothers can tell me the answer because i don’t understand the question

Raj encoded a secret phrase using matrix multiplication. using a = 1, b = 2, c = 3, and so on, he multiplied the clear text code for each letter by the matrix to get a matrix that represents the encoded text. the matrix representing the encoded text is . what is the secret phrase? determine the location of spaces after you decode the text. yummy is the corn the tomato is red the corn is yummy red is the tomato