Bills average on tests is 81. If he gets a 93, he will increase his average by about 2.5%. How many tests has Bill taken already?

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x^2 + 81

we can factor this using difference of square binomials.

rewrite the equation:

x^2 - (-81)

factor:

(a^2 - b^2) = (√a^2 + √b^2)(√a^2 - √b^2)

(x^2 - (-81) = (x + √-81)(x - √-81)

we can remove the - from under the radical by multiplying it by i.

(x^2 - (-81) = (x + i√81)(x - i√81)

(x^2 - (-81) = (x + 9i)(x - 9i)

we can check our answer by using foil:

x^2 - 9ix + 9ix - 81i^2

x^2 - 81^2

i^2 = -1

x^2 + 81

the graph is negative for all real values of x where   -6 < x < -2.

step-by-step explanation:

this refers to the values of f(x) in the area below the x-axis.

she made 48 + y = a cookies.     not enough info is given to find the total.