# Using the quadratic formula and determining whether two lines are parallel, perpendicular or neither

#### drop

##### New member
Basically I don't know anyone in real life that can help me with this, so I need help checking to see if my answers are correct

PART A

3) Solve 2x^2 + 4x = 15 by using the quadratic formula.

x = -1 +/- 2sqr34

4) Determine whether the given pairs of lines are parallel, perpendicular, or neither.

a) y = -4x + 3 b) x - 4y = 4

#### MarkFL

Staff member

3.) Incorrect.

We have:

$$\displaystyle 2x^2+4x-15=0$$

$$\displaystyle x=\frac{-4\pm\sqrt{(4)^2-4(2)(-15)}}{2(2)}=\frac{-4\pm\sqrt{136}}{4}=\frac{-4\pm2\sqrt{34}}{4}=\frac{-2\pm\sqrt{34}}{2}$$

We could choose to write this as:

$$\displaystyle x=-1\pm\sqrt{\frac{17}{2}}$$

4.)

a) Correct. The product of the slopes of the two lines is -1.