SOLUTION: Solve. w^4-20w^2-2=0 What is the solution? w=? (Type an exact answer, using radicals as needed. Use commas to separete answers aas needed)

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Question 623326: Solve.
w^4-20w^2-2=0
What is the solution?
w=?
(Type an exact answer, using radicals as needed. Use commas to separete answers aas needed)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I can say +z+=+w%5E2+ and
+w%5E4+-+20w%5E2+-+2+=+z%5E2+-+20z+-+2+
+z%5E2+-+20z+-+2+=+0+
Use quadratic formula
+z+=+%28-b+%2B-+sqrt%28+b%5E2+-+4%2Aa%2Ac+%29%29+%2F+%282%2Aa%29+
+a+=+1+
+b+=+-20+
+c+=+-2+
+z+=+%28-%28-20%29+%2B-+sqrt%28+%28-20%29%5E2+-+4%2A1%2A%28-2%29+%29%29+%2F+%282%2A1%29+
+z+=+%28+20+%2B-+sqrt%28+400+%2B+8%29%29+%2F+2+
+z+=+%28+20+%2B-+20.199%29+%2F+2+
+z+=+40.199%2F2+
+z+=+20.0995+
and
+z+=+-.199%2F2+
+z+=+-.0995+
--------------
+z+=+w%5E2+
+w+=+sqrt%28z%29+
+w+=+sqrt%28+20.0995+%29++
+w+=+4.4832+
and
+w+=+sqrt%28+-.0995+%29+
+w+=+.3154i+
-----------------
check answer:
+w%5E4+-+20w%5E2+-+2+=+0+
+.3154%5E4%2A+i%5E4+-+20%2A.3154%5E2+%2A+i%5E2+-+2+=+0+
+.009896+%2A+1+-+1.9895+%2A+%28-1%29+-+2+=+0+
+.009896+%2B+1.9895+-+2+=+0+
+1.9994+-+2+=+0+
+.00056+=+0+
error due to rounding off?
You can check other answer