SOLUTION: solve x^2+18x-4=0 simplify your answers. Use a comma to separate answers as needed. Type an exact answer, using radicals as needed. Type each solution only once.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: solve x^2+18x-4=0 simplify your answers. Use a comma to separate answers as needed. Type an exact answer, using radicals as needed. Type each solution only once.      Log On


   

Question 358140: solve x^2+18x-4=0 simplify your answers. Use a comma to separate answers as needed. Type an exact answer, using radicals as needed. Type each solution only once.
Answer by jsmallt9(3758) About Me  (Show Source):
You can put this solution on YOUR website!
x%5E2%2B18x-4=0
This is a quadratic equation. After you get one side to be zero, you either factor the non-zero side or use the Quadratic Formula. Since we already have one side equal to zero and since the non-zero side cannot be factored easily, we will go straight to the Quadratic Formula, x+=+%28-b+%2B-+sqrt%28b%5E2+-4ac%29%29%2F%282a%29, where the "a", "b" and "c" are from ax%5E2+%2B+bx+%2B+c+=+0. Your a=1, b=18 and c =-4. So
x+=+%28-%2818%29+%2B-+sqrt%28%2818%29%5E2+-+4%281%29%28-4%29%29%29%2F%282%281%29%29
Simplifying:
x+=+%28-%2818%29+%2B-+sqrt%28324+-+4%281%29%28-4%29%29%29%2F%282%281%29%29
x+=+%28-18+%2B-+sqrt%28324+%2B+16%29%29%2F2
x+=+%28-18+%2B-+sqrt%28340%29%29%2F2
x+=+%28-18+%2B-+sqrt%284%2A85%29%29%2F2
x+=+%28-18+%2B-+sqrt%284%29%2Asqrt%2885%29%29%2F2
x+=+%28-18+%2B-+2%2Asqrt%2885%29%29%2F2
x+=+%282%28-9+%2B-+sqrt%2885%29%29%29%2F2
x+=+%28cross%282%29%28-9+%2B-+sqrt%2885%29%29%29%2Fcross%282%29
x+=+-9+%2B-+sqrt%2885%29
In "long form" this is:
x+=+-9+%2B+sqrt%2885%29 or x+=+-9+-+sqrt%2885%29