SOLUTION: find all real solutions of the equations : (x^2 +1)^2 - 18( x^2 +1) = -17

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Question 462550: find all real solutions of the equations : (x^2 +1)^2 - 18( x^2 +1) = -17
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!
%28x%5E2+%2B1%29%5E2+-+18%28+x%5E2+%2B1%29+=+-17
x%5E4%2B2x%5E2+%2B1+-+18x%5E2+-1+=+-17
x%5E4+-16x%5E2+%2B17=0
%28x%5E2%29%5E2+-16x%5E2+%2B17=0...you can solve it as quadratic using quadratic formula, you will just have four solutions; both solutions as quadratic equation you will take positive i negative value of their square root
Solved by pluggable solver: Quadratic Formula
Let's use the quadratic formula to solve for x:


Starting with the general quadratic


ax%5E2%2Bbx%2Bc=0


the general solution using the quadratic equation is:


x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29




So lets solve x%5E2-16%2Ax%2B17=0 ( notice a=1, b=-16, and c=17)





x+=+%28--16+%2B-+sqrt%28+%28-16%29%5E2-4%2A1%2A17+%29%29%2F%282%2A1%29 Plug in a=1, b=-16, and c=17




x+=+%2816+%2B-+sqrt%28+%28-16%29%5E2-4%2A1%2A17+%29%29%2F%282%2A1%29 Negate -16 to get 16




x+=+%2816+%2B-+sqrt%28+256-4%2A1%2A17+%29%29%2F%282%2A1%29 Square -16 to get 256 (note: remember when you square -16, you must square the negative as well. This is because %28-16%29%5E2=-16%2A-16=256.)




x+=+%2816+%2B-+sqrt%28+256%2B-68+%29%29%2F%282%2A1%29 Multiply -4%2A17%2A1 to get -68




x+=+%2816+%2B-+sqrt%28+188+%29%29%2F%282%2A1%29 Combine like terms in the radicand (everything under the square root)




x+=+%2816+%2B-+2%2Asqrt%2847%29%29%2F%282%2A1%29 Simplify the square root (note: If you need help with simplifying the square root, check out this solver)




x+=+%2816+%2B-+2%2Asqrt%2847%29%29%2F2 Multiply 2 and 1 to get 2


So now the expression breaks down into two parts


x+=+%2816+%2B+2%2Asqrt%2847%29%29%2F2 or x+=+%2816+-+2%2Asqrt%2847%29%29%2F2



Now break up the fraction



x=%2B16%2F2%2B2%2Asqrt%2847%29%2F2 or x=%2B16%2F2-2%2Asqrt%2847%29%2F2



Simplify



x=8%2Bsqrt%2847%29 or x=8-sqrt%2847%29



So the solutions are:

x=8%2Bsqrt%2847%29 or x=8-sqrt%2847%29




So yoursolutions are:
x=sqrt%288%2B%28sqrt%2847%29%29%29+ or x=sqrt%288-%28sqrt%2847%29%29%29

x=sqrt%288%2B6.8556546%29+ or x=sqrt%288-6.8556546%29
x=sqrt%2814.8556546%29+ or x=sqrt%281.1443454%29
x=3.8543 or x=1.06974
so, your solutions are:
x=3.8543
x=-3.8543
x=1.06974
x=-1.06974

+graph%28+500%2C+500%2C+-5%2C+40%2C+-20%2C+40%2C+x%5E4+-16x%5E2+%2B17%29+