SOLUTION: I need help solving x4 -5x2 - 36=0 I am not sure what to do with x4

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Question 32364This question is from textbook Elementary and Intermediate alegbra
: I need help solving x4 -5x2 - 36=0 I am not sure what to do with x4 This question is from textbook Elementary and Intermediate alegbra

Answer by Cintchr(481) About Me  (Show Source):
You can put this solution on YOUR website!
First, always try and solve by factoring. This one happens to be factorable.
+x%5E4+-5x%5E2+-+36=0+
-9 * 4 = 36 and -9 + 4 = -5
+%28x%5E2+-9%29%28x%5E2+%2B+4%29+=0+
Continue factoring
+%28x-3%29%28x%2B3%29%28x%5E2%2B4%29=0+
Set each piece equal to zero
+x-3=0+ and +x%2B3+=+0+ and +x%5E2%2B4=0+
+x=3+ and +x=-3+ and +x%5E2+=+-4+
+x=3+ and +x=-3+ and +sqrt%28x%5E2%29+=+sqrt%28-4%29+
+x=3+ and +x=-3+ and +x+=+sqrt%28-4%29+
+x=3+ and +x=-3+ and +x+=+i%28sqrt%284%29%29+
+x=3+ and +x=-3+ and +x+=+2i+
assuming your instructor wants ONLY real roots, then x = {3, -3 }
If s/he wants all roots ... x = { -3, 3, 2i }