# A Cry for Help

1. Oct 12, 2006

### Erectable

I might not be the brightest bob in the bunch but I am having trouble with a simple quadratic equation.

k^2 + (k + 4)^2 = 346

According to my manual expands to:

k^2 + k^2 + 8k + 16 = 346

Everything is going fine until I see the 8k. Where did the 8k come from? Or is my manual wrong?

If anyone is willing to aid a poor soul with his maths I would be very grateful.

2. Oct 12, 2006

Hmm...

$$k^2 + (k+4)^2 = 346$$

When you square k+4, please remember that it is not $$k^2 + 16$$, but rather $$(k+4)(k+4)$$, which is a polynomial. After you finish using the FOIL method, you get $$k^2 + 4k + 4k + 16$$, which can be simplified to $$k^2 + 8k + 16$$, which is how you get your 8k.

The solution to the problem is 11 (Quadratic Equation).

Besides... are you in 9th grade?

3. Oct 12, 2006

### biggins

yes

Because (k + 4) ^2 = (k+4)(k+4) and you cant just multiply k*k and add it to 4*4 you have to multiply each element as in: k*k + k*4 + k*4 +4*4 which will give you k^2 + 8k + 16. so if you had (k+ 3)(k + 2) = k^2 + 2*k + 3*k + 6