What number must be added to the expression below to complete the
square?
x² - 18x​

+81

Step-by-step explanation:

remember the formula (a-b)^2=a^2+b^2-2ab

x^2=a^2

-18x=-2*a*b

and you're trying to find b^2

you can get b from the 2*a*b

if -2*a*b=-18x, well you can remove a and x first, so -2b=-18 and b=9

9^2 is 81

answer

explanation

the area of a circle is calculated using the formula

or

we can use any of the above formulae to calculate the required. preferably, let us use the latter since the diameter is

we substitute the diameter into the formula to get:

this is the exact value for the area of the circle.

the correct answer is a

1,645,493,059.35

step-by-step explanation: