SOLUTION: use the quadratic formula to solve the following equations (r-2)(r+6)=11 simplify your answer. type an exact answer using radicals as needed. use integers or fractions for an

Algebra ->  Radicals -> SOLUTION: use the quadratic formula to solve the following equations (r-2)(r+6)=11 simplify your answer. type an exact answer using radicals as needed. use integers or fractions for an      Log On


   

Question 547137: use the quadratic formula to solve the following equations
(r-2)(r+6)=11
simplify your answer. type an exact answer using radicals as needed. use integers or fractions for any numbers in the expression. use a comma to seperate answers as needed.
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
(r-2)(r+6)=11
r(r+6)-2(r+6)+11=0
r^2+6r-2r-12+11=0
r^2+4r-1=0
Find the roots of the equation by quadratic formula

a= 1 ,b= 4 ,c= -1

b^2-4ac= 16 + 4
b^2-4ac= 20
x=%28-b%2B-sqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-b%2Bsqrt%28b%5E2-4ac%29%29%2F%282a%29
x1=%28-12%2B21%29%2F%282%29
x1=( -4 + 4.47 )/ 2
x1= 0.24
x2=( -4 -4.47 ) / 2
x2= -4.24
you can also work it out in fractions