How do you solve 6x^2-8x-3=0 using the quadratic formula?

2 Answers
Mar 13, 2016

x_(1,2) = (-color(blue)8+- sqrt(color(blue)(64)-72))/(12)= -2/3 +- isqrt(2)/6 = 1/3(-2+-sqrt(2)/2)
Note this means:
x_1 = 1/3 (-2+sqrt(2)/2) and x_1 = 1/3 (-2-sqrt(2)/2)

Explanation:

I suggest you commit to memory the "Quadratic Formula" it probably one of the formula that you absolutely positively must know by heart: So here is your Quadratic Formula:
Given a 2nd Order Polynomial,P_2:

P_2 = color(red)ax^2 + color(blue)bx + color(green)c the Roots or solutions to the equation
x_1 and x_2 are given by the Quadratic Formula:

x_(1,2) = (-color(blue)b+- sqrt(color(blue)(b^2)-4color(red)acolor(green)c))/(2color(red)a)

Now for your equation: color(red)6x^2-color(blue)8x-color(green)3=0

x_(1,2) = (-color(blue)8+- sqrt(color(blue)(8^2)-4*color(red)6*color(green)3))/(2*color(red)6)
x_(1,2) = (-color(blue)8+- sqrt(color(blue)(64)-72))/(12)= -2/3 +- isqrt(2)/6 = 1/3(-2+-sqrt(2)/2)

Mar 16, 2016

x=(4+-sqrt(34))/6

Explanation:

1. Since the given equation is already in standard form, identify the color(blue)a,color(darkorange)b, and color(violet)c values. Then plug the values into the quadratic formula to solve for the roots.

color(blue)6x^2 color(darkorange)(-8)x color(violet)(-3)=0

color(blue)(a=6)color(white)(XXXXX)color(darkorange)(b=-8)color(white)(XXXXX)color(violet)(c=-3)

x=(-b+-sqrt(b^2-4ac))/(2a)

x=(-(color(darkorange)(-8))+-sqrt((color(darkorange)(-8))^2-4(color(blue)6)(color(violet)(-3))))/(2(color(blue)6))

x=(8+-sqrt(64+72))/12

x=(8+-sqrt(136))/12

x=(8+-2sqrt(34))/12

2. Factor out 2 from the numerator and denominator.

x=(2(4+-sqrt(34)))/(2(6))

x=(color(red)cancelcolor(black)2(4+-sqrt(34)))/(color(red)cancelcolor(black)2(6))

color(green)(|bar(ul(color(white)(a/a)x=(4+-sqrt(34))/6color(white)(a/a)|)))