SOLUTION: 3a^2+a-10>0 we are using delta = b^2-4*a*c my solution to this equation is [-5/2,3} the book says the solution is (-oo,-2)U(5/3,oo) please help me find what I am doing wrong

Algebra ->  Inequalities -> SOLUTION: 3a^2+a-10>0 we are using delta = b^2-4*a*c my solution to this equation is [-5/2,3} the book says the solution is (-oo,-2)U(5/3,oo) please help me find what I am doing wrong       Log On


   



Question 264297: 3a^2+a-10>0
we are using delta = b^2-4*a*c
my solution to this equation is [-5/2,3} the book says the solution is (-oo,-2)U(5/3,oo)
please help me find what I am doing wrong

Found 2 solutions by mananth, ikleyn:
Answer by mananth(16949) About Me  (Show Source):
You can put this solution on YOUR website!
3a^2+a-10>0
we are using delta = b^2-4*a*c
my solution to this equation is [-5/2,3} the book says the solution is (-oo,-2)U(5/3,oo)
please help me find what I am doing wrong
3a^2+a-10>0
3a^2+6a-5a-10>0
3a(a+2)-5(a+2)>0
(a+2)(3a-5)>0



Answer by ikleyn(53751) About Me  (Show Source):
You can put this solution on YOUR website!
.

Your error is that you treat it as an equation and find the roots of the equation,
while in the problem, you are given an inequality and should treat it as an inequality.