## cbAuroraIn 3 years ago I'm trying to solve 2x^2+11x-21 by quadratic formula. Factoring gives 3/2, -7, but by the formula (which should always work), I get: (-11/4)+/-((22/4)(42)^(1/2)). Can anyone help me spot my stupid error?

1. lalaly

are u still there?

2. mominanisar

factoring gives 3/2, -7, the quadratic formula is x=(-b±sqrt(b^2-4ac))/2a from your equation a=2,b=11,c=-21 put values in formula x=(-11±sqrt(121-(168)))/2x2 x=(-11±sqrt(289))/4 x=(-11±17)/4. x=3/2, -7

3. jhonyy9

so if factoring this is right (2x-3)(x+7)=2x2+11x-21 so than your got solutions x=3/2 and x=-7 is right,correct sure always

4. jhonyy9

mominanisar ATTENTION in this calcules are some errore because inside squarroot there not is minus 168 correct,right is plus 168 and in thgis way will get these correct factorized resultes

5. jhonyy9

6. mominanisar

i am seriously sorry actually this step is likex=(-11±sqrt(121-(168)))/2x2 new onex=(-11±sqrt(121-(-168)))/2x2 because 'c' is minus

7. mominanisar

it is a typing mistake by me

8. cbAuroraIn

Thanks!