I have a math question I don't get.?

Question

It goes 3x(squared)-39x= -126 and it asks Solve for x

How do I do this?

Answer 1

3x(squared)-39x= -126

I assume you mean: 3x² - 39x = -126

let 3x² - 39x +126 = 0
factoring,
3x........-21.......-21x
x............-6........-18x
----------------------------
3x².....+126......-39x.

3x² - 39x +126 = 0
(3x - 21)(x - 6 ) = 0
3x - 21 = 0....or..... x - 6 =0
3x = 21.........or.......x = 6
x = 21/3 = 7

Answer 2

It's a question of Quadratic Equations. It think the easiest way of solving it is by factorisation -

3x^2 - 39x = -126 [ x^2 means x squared]
3x^2 - 39x + 126 = 0 [ Taking -126 on the LHS]
x^2 - 13x + 42= 0 [Dividing the eqn throughout by 3 ]

Now, you need any two real numbers whose product is 42 and sum is -13.

The nos. can be found by Trial-an-Error Method..

The nos are -6 and -7....Because (-6)*(-7) = 42 and (-6) + (-7) = -13

From the equation,
x^2 - 6x - 7x + 42 = 0
x (x-6) - 7 (x - 6) = 0 [ By factorising x which is common]
(x - 6) (x - 7) = 0 [ By factorising (x-6) which is common]

Now, if u divide the equation by (x-6), then
x-7=0
Hence, x=7..

And, if u divide the equation by (x-7), then
x-6=0

Hence, x = 6

Finally, both 6 and 7 are solutions..
Therefore, x= 6 and 7.

Answer 3

Given equation........

3x^2 - 39x = -126
3x^2 - 39x + 126 = 0

Divide the equation by 3.........

x^2 - 13x + 42 = 0
(x-6) (x-7) = 0
x = 6 or 7

Answer 4

This is a quadratic equation.
Rewrite as 3x^2-39x+126=0
Divide by 3: x^2-13x-42=0
Factor: (x-6)(x-7)=0
Solve: x=6, x=7
You could have used the quadratic formula to find the roots, but it is easier to factor when possible.

Answer 5

3x^2 - 39x = -126

Equating the equation to 0......
3x^2 - 39x + 126 = 0

Dividing throughout by 3......
x^2 - 13x + 42 = 0

Factorising the equation......
(x - 7)(x - 6) = 0

x = 7 or x = 6

Answer 6

solve like this
move 126 to the other side

3x(sq)-39x+126=0

factor our a 3

3(x(sq)-13x-42)=0

then
3(x-7)(x-6)=0
so
x-7=0
x=7
and
x-6=0
x=6
If you have a problem figuring out the -7 and -6, do a search on the quadratic formula ( I can not think of an easy way to represent it here)

Answer 7

use quadratic formula

3x^2 - 39x + 126 = 0

[39 + sqrt(39^2 - (4 * 3 * 126))]/6

[39 - sqrt(39^2 - (4 * 3 * 126))]/6

x = 7 , 6

Answer 8

3x^2 - 39x = -126

First, let's divide each side by 3:

x^2 - 13x = -42

Next, add 42 to each side:

x^2 - 13x + 42 = 0

Next, factor into:

(x - 7)(x - 6) = 0

Now, solve for x:

x = 6 or 7

Answer 9

quadratic formula