Which choice is equivalent to the expression below? square root of -81

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 .

geometry: triangles

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call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

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