Answer: a) x = {-3, 3, -3i, 3i}
b) x = {-√5, √5}
c) x = {-√3, √3, -i√2, i√2}
<u>Step-by-step explanation:</u>
![a)\ x^4-81=0\\\\(x^2-9)(x^2+9)=0\\\\x^2=9\quad and\quad x^2=-9\\\\x=\pm 3\quad and\quad x=\pm3i](https://tex.z-dn.net/?f=a%29%5C%20x%5E4-81%3D0%5C%5C%5C%5C%28x%5E2-9%29%28x%5E2%2B9%29%3D0%5C%5C%5C%5Cx%5E2%3D9%5Cquad%20and%5Cquad%20x%5E2%3D-9%5C%5C%5C%5Cx%3D%5Cpm%203%5Cquad%20and%5Cquad%20x%3D%5Cpm3i)
![b)\ x^4+10x^2+25=0\\\\(x^2+5)^2=0\\\\x^2=-5\\\\x=\pm i\sqrt5](https://tex.z-dn.net/?f=b%29%5C%20x%5E4%2B10x%5E2%2B25%3D0%5C%5C%5C%5C%28x%5E2%2B5%29%5E2%3D0%5C%5C%5C%5Cx%5E2%3D-5%5C%5C%5C%5Cx%3D%5Cpm%20i%5Csqrt5)
![c)\ x^4-x^2-6=0\\\\(x^2-3)(x^2+2)=0\\\\x^2-3=0\quad and\quad x^2+2=0\\\\x^2=3\qquad and\quad x^2=-2\\\\x=\pm\sqrt3\quad and\quad x=\pm i\sqrt2](https://tex.z-dn.net/?f=c%29%5C%20x%5E4-x%5E2-6%3D0%5C%5C%5C%5C%28x%5E2-3%29%28x%5E2%2B2%29%3D0%5C%5C%5C%5Cx%5E2-3%3D0%5Cquad%20and%5Cquad%20x%5E2%2B2%3D0%5C%5C%5C%5Cx%5E2%3D3%5Cqquad%20and%5Cquad%20x%5E2%3D-2%5C%5C%5C%5Cx%3D%5Cpm%5Csqrt3%5Cquad%20and%5Cquad%20x%3D%5Cpm%20i%5Csqrt2)
Answer:
42
Step-by-step explanation:
![\boxed{ \bold{formula = \pi \times d}}](https://tex.z-dn.net/?f=%20%5Cboxed%7B%20%5Cbold%7Bformula%20%3D%20%5Cpi%20%5Ctimes%20d%7D%7D)
22/7 × d = 132
d = 132 : 22/7
d = 132 × 7/22
d = 6× 7
d = 42
Since we need your monthly bill we will call it the variable B for now, (Unless you have the bill, if so replace it with the variable)
Multiply 1.64 x B since the exchange rate is different than the US bill,
For example, say your bill is $100 in the U.S.
You do 1.64 x 100 = A monthly bill of $164 if you lived in Britain
7^2 = 6^2 + 9^2 - 2(6)(9)cos(m)
-68 = 2(6)(9)cos(m)
cos(m) = -0.6296
m = arcos ( -0.6296)
m = 129.0 degrees
Tayler money ................... 320$
Estimated cost per chair....80$
Friend's chairs..................3
Total chairs..........> cc
cc = 320$/80$ +3
cc = 4 + 3 = 7 chairs