Uhhh help me , i give brainliest

36

Step-by-step explanation:

x² + 12x - 40 = 0

x² + 12x    = 40

Now, 12/2 = 6. So add 6² = 36 to each side

x² + 12x + 36 = 40 +36

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

b and c

step-by-step explanation: