Use the quadratic formula to find the roots of the equation. x^2 + 3x - 18 = 0
A. {-6, 3}
B. {-2, 9}
C. {-3, 6}
D. {-9, 2}

Question

Use the quadratic formula to find the roots of the equation. x^2 + 3x - 18 = 0
	A.	{-6, 3}
	B.	{-2, 9}
	C.	{-3, 6}
	D.	{-9, 2}

jhonyy9 · Answer

=(x-3)(x+6)
x_1=3
x_2=-6

jhonyy9 · Answer

A. is right

anonymous · Answer

x^2 + 3x - 18 
= -3 +/- the square root of ((3)^2 - (-18)(4)(1) all over 2(1))
= -3 +/- the square root of (9 + 72) all over 2
= -3 +/- the square root of 81 all over 2
= -3 +/- 9 all over 2
= 6/2 and -12/2 
= 3 , -6
A is the correct answer

anonymous · Answer

$$\LARGE \text{Use:} \;\;\; x_{1/2}=\frac{-b\pm \sqrt{b^2-4ac}}{2a}$$

so we have...

$$\LARGE x_{1/2}=\frac{-3\pm \sqrt{3^2-4\cdot 1 \cdot (-18)}}{2\cdot 1}$$

$$\LARGE x_{1/2}=\frac{-3\pm \sqrt{81}}{2}$$

$$\LARGE x_{1/2}=\frac{-3\pm 9}{2}$$

$$\LARGE x_1 =3 ,    \;\;\;\;\; x_2=-6$$