Hiii, I have a little maths problem. So I have this at the photo. I checked and the answer should be -0,0081 . But I don't get why is it with a minus cuz a rule says: if ,,a" is a negative number and the degree is an even number then we should make the final number positive but here it's negative. I don't get why. I'll give brainliest if you can help me!

Hiii I have a little maths problem So I have this at the photo I checked and the answer should be 00081 But I dont get why is it with a minus cuz a rule says if class=