Thursday

January 29, 2015

January 29, 2015

Posted by **Lee** on Wednesday, October 31, 2012 at 10:51am.

-3x^2+9x=1

Not sure how to do these, if someone could expplain.

- algebra -
**Steve**, Wednesday, October 31, 2012 at 12:01pmit's usually easier to have a positive coefficient for x^2, so let's take care of that first:

3x^2 - 9x = -1

x^2 - 3x = -1/3

since (x-a)^2 = x^2 - 2a + a^2, you want to take half of 3 and square it, then add that to both sides:

x^2 - 3x + 9/4 = -1/3 + 9/4

Now you have a perfect square on the left:

(x-3/2)^2 = 23/12

now take square roots:

x - 3/2 = ±√(23/12) = ±√69/6

so,

x = 3/2 ±√69/6

or,

x = (9±√69)/6

Note how that is the solution using the quadratic formula.

- algebra -
**Lee**, Wednesday, October 31, 2012 at 9:35pmStill confused, but I'll try another one and see if I get it. Thank you.

**Answer this Question**

**Related Questions**

math,help,algebra I - I need help can someone help me get unstuck and let me ...

Algebra 2 - Completing the square method allows you to solve any quadratic ...

Algebra - Which of the following statements is true? A. Any quadratic equation ...

Algebra - How do I solve a quadratic equation x^2 - x = 30 by completing the ...

Algebra - I was given this answers to a problems I solved but I do not ...

Algebra - I was given this answers to a problems I solved but I do not ...

Math - Hi everyone. Would someone be able to help me with this problems? I know ...

algebra - solve the quadratic equation by completing the square -3x^2+9=1

HELP ! Algebra - Solve the quadratic equation by completing the square. (-x^2 + ...

Math - Algebra - A. Solve the following quadratic equations. Make sure to show ...