SOLUTION: please solve 2x^2-5x-7 using the quadratic equation.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: please solve 2x^2-5x-7 using the quadratic equation.      Log On


   

Question 298951: please solve 2x^2-5x-7 using the quadratic equation.
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!

2x%5E2-5x-7=0 Start with the given equation.


Notice that the quadratic 2x%5E2-5x-7 is in the form of Ax%5E2%2BBx%2BC where A=2, B=-5, and C=-7


Let's use the quadratic formula to solve for "x":


x+=+%28-B+%2B-+sqrt%28+B%5E2-4AC+%29%29%2F%282A%29 Start with the quadratic formula


x+=+%28-%28-5%29+%2B-+sqrt%28+%28-5%29%5E2-4%282%29%28-7%29+%29%29%2F%282%282%29%29 Plug in A=2, B=-5, and C=-7


x+=+%285+%2B-+sqrt%28+%28-5%29%5E2-4%282%29%28-7%29+%29%29%2F%282%282%29%29 Negate -5 to get 5.


x+=+%285+%2B-+sqrt%28+25-4%282%29%28-7%29+%29%29%2F%282%282%29%29 Square -5 to get 25.


x+=+%285+%2B-+sqrt%28+25--56+%29%29%2F%282%282%29%29 Multiply 4%282%29%28-7%29 to get -56


x+=+%285+%2B-+sqrt%28+25%2B56+%29%29%2F%282%282%29%29 Rewrite sqrt%2825--56%29 as sqrt%2825%2B56%29


x+=+%285+%2B-+sqrt%28+81+%29%29%2F%282%282%29%29 Add 25 to 56 to get 81


x+=+%285+%2B-+sqrt%28+81+%29%29%2F%284%29 Multiply 2 and 2 to get 4.


x+=+%285+%2B-+9%29%2F%284%29 Take the square root of 81 to get 9.


x+=+%285+%2B+9%29%2F%284%29 or x+=+%285+-+9%29%2F%284%29 Break up the expression.


x+=+%2814%29%2F%284%29 or x+=++%28-4%29%2F%284%29 Combine like terms.


x+=+7%2F2 or x+=+-1 Simplify.


So the solutions are x+=+7%2F2 or x+=+-1