Question

solving 3x^2=15x+10 my answer is 15+-sqrt of 105/6. is this correct? i used the quadratic formula. or is there a more efficient way?

Answer 1

coll... guy !
hmm......

Answer 2

the 2nd one!

Answer 3

yup.. having issues..lol

Answer 4

Completing the square will work too,
\[3x^2-15x-10=0\]
\[3(x^2-5x)-10=0\]
\[3(x-\frac{5}{2})^2-\frac{25}{4}(3)-10=0\]
\[3(x-\frac{5}{2})^2-\frac{115}{4}=0\]
\[3(x-\frac{5}{2})^2=\frac{115}{4}\]
\[(x-\frac{5}{2})^2=\frac{115}{12}\]
\[x-\frac{5}{2}=\pm\frac{\sqrt{345}}{6}\]
\[x=\frac{5}{2}\pm\frac{\sqrt{345}}{6}\]