Can someone explain how the application of this formula:

$$x2+px+q=0$$
$$x=-p/2 +- \sqrt{(p/2)^2 - q}$$

To this problem:

$$7x^2 - 5x -2$$

Becomes this in factor form:
$$7(x-1)(x+2/7)$$

Question

Can someone explain how the application of this formula:

$$x2+px+q=0$$
$$x=-p/2 +- \sqrt{(p/2)^2 - q}$$

To this problem:

$$7x^2 - 5x -2$$

Becomes this in factor form:
$$7(x-1)(x+2/7)$$

anonymous · Answer

$$7x^2-5x-2=0$$divide both sides by 7$$x^2-\frac{5}{7}x-\frac{2}{7}=0$$now u can apply that formula

anonymous · Answer

I tried that but I keep getting it wrong... :/

anonymous · Answer

what u got ??

anonymous · Answer

$$x^2-5x/7-2/7$$
$$(5x/7)/2 +- \sqrt{((5x/7)/2)^2 + 2/7}$$
$$x1: (5x/7)/2 - (5x/7)/2 + \sqrt{2/7} =  \sqrt{2/7}$$

I should get 2/7 though, not  sqrt{2/7}

anonymous · Answer

dude what did u do ???

anonymous · Answer

p=-5/7
q=-2/7

anonymous · Answer

Ehm... wish I knew :)

anonymous · Answer

q = -(-2/7), isn't it? So +2/7

anonymous · Answer

$$x=-p/2 +- \sqrt{(p/2)^2 - q}=5/14 +- \sqrt{(5/14)^2 +2/7}$$

anonymous · Answer

firstly tell me why u dont use$$x=\frac{-b\pm\sqrt{b^2-4ac}}{2a}$$??

anonymous · Answer

because this chapter is about learning the x2+px+q=0 formula

anonymous · Answer

ok

anonymous · Answer

although, the quadratic formula seems far better suited to this problem

anonymous · Answer

u cant seperate radical like that :|

anonymous · Answer

$$5/14 \pm \sqrt{(5/14)^2 +2/7}=5/14 \pm \sqrt{81/196}=5/14 \pm 9/14$$

anonymous · Answer

wow... thanks, I can see I'm starting to get tired. This shouldn't be so hard. :/

anonymous · Answer

yeah :) no problem