Solve 6x² + 3x – 18 = 0 using the quadratic formula. ?

Question

Solve 6x² + 3x – 18 = 0 using the quadratic formula. ?

Answer 1

you don't have to use formula at all

First factor out 3, so you eqation will be

2x^2+x-6=0

(2x-3)(x+2)=0

x=3/2 or x=-2

Answer 2

Instead of using the formula, I would divide it by 6 and come down to x^2 + 0.5x - 3 = 0

Then split the equation as x^2 +2x -1.5x -3=0

Then x(x+2) -1.5(x+2) = 0

Therefore (x-1.5) (x+2) = 0

so, x = 1.5 or x = -2

All the best

Answer 3

Negative B plus or minus the square root of  B squared minus 4AC all over 2A, where the formula is AX^2 + BX + C. Just plug in the values. Look at this place for extra help:

http://www.purplemath.com/modules/quadfo...

Answer 4

2x² + x - 6 = 0

x = [ - 1 ± √ (1 + 48 ) ] / 4

x = [ - 1 ± √ (49) ] / 4

x = [ - 1 ± 7 ] / 4

x = 6/4 , x = - 2

x = 3/2 , x = - 2

Answer 5

6x^2 + 3x - 18 = 0

(6x^2 + 3x - 18)/3 = 0/3

2x^2 + x - 6 = 0

x = [-b ±√(b^2 - 4ac)]/2a

a = 2

b = 1

c = -6

x = [-1 ±√(1 + 48)]/4

x = [-1 ±√49]/4

x = [-1 ±7]/4

x = [-1 + 7]/4

x = 6/4

x = 3/2 (1.5)

x = [-1 - 7]/4

x = -8/4

x = -2

∴ x = -2 , 3/2 (1.5)

Answer 6

the quadratic formula is:

         -b ± SQRT(b2 - 4ac)

    x = -----------------------------

                2a

the general formula of a quadratic equation is:

ax2 + bx + c = 0, which is equivalet to  6x² + 3x – 18 = 0

where,

a= 6, b=3, c=-18

Using the formula:

         -b ± SQRT(b2 - 4ac)

    x = ------------------------------

                2a

we substitute the value in, which gives us:

          -3 ± SQRT((3)2 - 4(6)(-18)

    x = -------------------------------------

                2(6)

          -3 ± SQRT(9 +432)

    x = -----------------------------

                12

         -3 ± SQRT(441)

    x = ------------------------

                12

          -3 ± 21

    x = --------------

             12

            

             -3+21            -3-21

    x = -----------    or ------------

               12               12

    x =  1.5         or    -4

i hope this helps :)

Answer 7

(2x-3)(3x+6)=0

therefore x =1.5 or -2

Answer 8

firstly, u can plot it into a graph.

secondly, do it algebraically.

here is the way to solve it algebraically:

6x² + 3x – 18 = 0

factorise it:

3(2x² + x – 9) = 0

(2x² + x – 9) = 0

factors of -6 (coefficient of c)

1, -6

2, -3

-1, 6

-2, 3

factors of 2 (coefficient of x²)

1, 2

thus, we have to find either

(1*1)+(-6*2)

OR

(1*2)+(-6*1)

OR

(-1*1)+(6*2)

OR

(-1*2)+(6*1)

OR

(-2*2)+(3*1)

OR

(3*2)+(-2*1)

OR

(2*2)+(-3*1)

OR

(-3*2)+(2*1)

(rmb that factor of 2 on the right)

(factor of -6 on the left)

= coefficient of x.

thus, (2*2)+(-3*1) = 1

therefore

(x + 2)(2x - 3) = 0

x = -2 OR 3

Answer 9

x = (-3 + sqrt(3^2 - 4 * 6 * 18)) / (2 * 6)   =  -0.25 + 1.71391365 i

x = (-3 + sqrt(3^2 - 4 * 6 * 18)) / (2 * 6)   =  -0.25 - 1.71391365 i

the above are the values of x

see the source link for explanation

Answer 10

The quadratic formula is x = (-b±√(b^2-4ac))/2a

where the general quadratic equation is y=ax^2 +bx + c.

So to solve your equation you need to sub b=3 a-6 and c=-18 into the quadratic formula.  

x = (-3±√(3^2-4(6)(-18)))/(2(6))

x = (-3±√441)/12

x = (-3+√441)/12 = 1.5   and x = (-3-√441)/12 = -2

Answer 11

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

x = (-3 +/- square root(3^2 - 4 * 6 * -18)) / (2 * 6)

x = (-3 +/- square root(9 - (-432) )) / 12

x = (-3 +/- square root(441)) / 12

x = (-3 +/- 21) / 12

x = -24 / 12 or x = 18 / 12

x = -2 or x = 1.5