You have a to pay 100 dollars but it is 20% off

It is 80 dollars $80

Step-by-step explanation:

100/5 = 20

100-20

=80

answer:

Square root of 81 is +/-9, then you add in the negative and it's still +/-9. If the negative were inside the radical then the answer would simply be 9i.

>>Any number times itself is a positive number (or zero), so you can't ever get to a negative number by squaring. Since square roots undo squaring, negative numbers can't have square roots.

>>TL;DR: It's undefined, or doesn't exist/is an imaginary number, because you can't take the square root of a negative number. A square is the result of a number, multiplied by itself; when the two are whole numbers, the result is a perfect square. For example, 16 is a square - 4*4 = 16 - and so is 25 - 5*5 = 25.

>>81=9⋅9 then the square root of √81=9 . Because the double multiplication for the same sign is always positive, the square root is also valid with the other sign 81=(−9)⋅(−9) then √81=−9 and we can say that √81=±9 .

Step-by-step explanation:

Explanation: To find the square root of 81 , or √81 , we have two find one number, that when multiplying itself, equals to 81 . That number is 9→ (9⋅9=81) Therefore √81=9 .