SOLUTION: Use the quadratic formula to solve the following equations 2x^2 - (/7)x - 1 = 0

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Use the quadratic formula to solve the following equations 2x^2 - (/7)x - 1 = 0      Log On


   

Question 101330: Use the quadratic formula to solve the following equations
2x^2 - (/7)x - 1 = 0
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
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 2x%5E2-sqrt%287%29x-1=0 ( notice a=2, b=-sqrt%287%29, and c=-1)




Plug in a=2, b=-sqrt%287%29, and c=-1


x+=+%28sqrt%287%29+%2B-+sqrt%28+%28-sqrt%287%29%29%5E2-4%2A2%2A-1+%29%29%2F%282%2A2%29 Negate -sqrt%287%29 to get sqrt%287%29


x+=+%28sqrt%287%29+%2B-+sqrt%28+7-4%2A2%2A-1+%29%29%2F%282%2A2%29 Square -sqrt%287%29 to get 7


x+=+%28sqrt%287%29+%2B-+sqrt%28+7%2B8+%29%29%2F%282%2A2%29 Multiply -4%2A2%2A-1 to get 8



x+=+%28sqrt%287%29+%2B-+sqrt%28+15+%29%29%2F%282%2A2%29 Add


x+=+%28sqrt%287%29+%2B-+sqrt%28+15+%29%29%2F%284%29 Multiply


x+=+%28sqrt%287%29+%2B+sqrt%28+15+%29%29%2F%284%29 or x+=+%28sqrt%287%29+-+sqrt%28+15+%29%29%2F%284%29 Break up the expression


So the answer is:

x+=+%28sqrt%287%29+%2B+sqrt%28+15+%29%29%2F%284%29 or x+=+%28sqrt%287%29+-+sqrt%28+15+%29%29%2F%284%29