Can someone get me started? solve x^2 - 9x - 4 = 6

[jdruopp]

I have done about 15 of these quadratic equations and have had no problem. Then I came upon this one. We can solve it with any technique.

x^2 - 9x -4 =6

According to the teacher the answers are -1, and 10.
But I keep getting crazy answers with fractions and radicands.
Can anyone help me through it?

 

[galactus]

Hello jdruopp:

Let's factor:

\(\displaystyle \L\\x^{2}-9x-4=6\)

\(\displaystyle \L\\x^{2}-9x-10=0\)

What two numbers when added equal -9 and when multiplied equal -10.

Ummm, let's see, maybe -10 and 1?.

\(\displaystyle \L\\x^{2}-10x+x-10\)

\(\displaystyle \L\\x(x-10)+(x-10)\)

Now, see it?.

Try using the quadratic formula and/or completing the square. See if you get the same. You should.

 

[jdruopp]

guess i was looking to much into it. sometimes the easy ones are the hardest to see. I feel silly now
thanks though

 

[stapel]

I keep getting crazy answers with fractions and radicands.

For future reference: If you show your work, then the tutors can help you find any errors in techniques and concepts, which will help you avoid making similar errors in the future (such as on tests).

Thank you.

Eliz.