solve for x; x^2+4x-21=0 show the steps please?

Answer 1

x^2 + 4x - 21 = 0
(x + 7)(x - 3) =0

x + 7 = 0
x = -7

x - 3 = 0
x = 3

Answer 2

x^2 + 4x - 21 = 0

To factor quadratics, you have to look at the coefficient of x and the constant term. The coefficient of x is 4, and the constant term is -21.

Here's where you ask yourself: What two numbers multiply to make -21 and add to make 4? The answer to that is +7 and -3, since
(7)(-3) = -21, and 7 + (-3) = 4. Therefore, we plug in 7 and -3, for

(x + ?)(x + ?) = 0
(x + 7)(x - 3) = 0

Now that we have a product of binomials equal to 0, we equate each of these to 0

x + 7 = 0
x - 3 = 0

Solving these individually, we will have x = -7 , x = 3

Therefore, we have TWO solutions:
x = {-7, 3}

Answer 3

x^2 + 4x - 21 = 0

x^2 + 4x - 21 = (x + 7)(x - 3) = 0
(x + 7)(x - 3) = 0

When x = -7,
(-7 + 7)(-7 -3) = 0
(0)(-10) = 0

When x = 3,
(3 + 7)(3 - 3) = 0
(10) (0) = 0

x^2 + 4x - 21 = 0, when x = -7 or x = 3

Answer 4

X^2 +4X - 21 = 0

(x + 7) (X - 3) = 0

X = -7

X = 3

Answer 5

Factor out, what terms multiply to give -21 and add to give +4?
(7)(-3), So, Factor:
(x+7)(x-3)=0
So x must either equal 3 or 7 in order for the answer to be 0.
x = 3; x = 7.

Answer 6

you have to use the following formula:

[ -b + or - square root of (b^2 - 4ac) ] / 2a

so u would have two answers:

A) (-4 + 10) / 2 = 3

B) (-4 - 10) / 2 = -7

Answer 7

(x + 7)(x - 3) = 0
x + 7 = 0 i.e x= -7
or
x - 3 = 0 i.e x = 3

x = {-7, 3}