SOLUTION: Solve by using the quadratic formula. 5x^2+5x=3 a. -5+-square root 85 over 10 b. -5+-square root 85 over 5 c. -5+-square root 40 over 5 d. -5+-square root 40 over 10

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: Solve by using the quadratic formula. 5x^2+5x=3 a. -5+-square root 85 over 10 b. -5+-square root 85 over 5 c. -5+-square root 40 over 5 d. -5+-square root 40 over 10       Log On


   

Question 102583: Solve by using the quadratic formula. 5x^2+5x=3
a. -5+-square root 85 over 10
b. -5+-square root 85 over 5
c. -5+-square root 40 over 5
d. -5+-square root 40 over 10
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
5x%5E2%2B5x=3 Start with the given equation


5x%5E2%2B5x-3=0 Subtract 3 from both sides




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 5%2Ax%5E2%2B5%2Ax-3=0 ( notice a=5, b=5, and c=-3)




x+=+%28-5+%2B-+sqrt%28+%285%29%5E2-4%2A5%2A-3+%29%29%2F%282%2A5%29 Plug in a=5, b=5, and c=-3



x+=+%28-5+%2B-+sqrt%28+25-4%2A5%2A-3+%29%29%2F%282%2A5%29 Square 5 to get 25



x+=+%28-5+%2B-+sqrt%28+25%2B60+%29%29%2F%282%2A5%29 Multiply -4%2A-3%2A5 to get 60



x+=+%28-5+%2B-+sqrt%28+85+%29%29%2F%282%2A5%29 Combine like terms in the radicand (everything under the square root)




x+=+%28-5+%2B-+sqrt%2885%29%29%2F10 Multiply 2 and 5 to get 10


So our answer is:


x+=+%28-5+%2B-+sqrt%2885%29%29%2F10


which means the answer is A