x^2+12x=-21

Simple and best practice solution for x^2+12x=-21 equation. Check how easy it is, and learn it for the future. Our solution is simple, and easy to understand, so don`t hesitate to use it as a solution of your homework.

If it's not what You are looking for type in the equation solver your own equation and let us solve it.

Solution for x^2+12x=-21 equation:


Simplifying
x2 + 12x = -21

Reorder the terms:
12x + x2 = -21

Solving
12x + x2 = -21

Solving for variable 'x'.

Reorder the terms:
21 + 12x + x2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + 12x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 12x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + 12x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 12x + x2 = 0 + -21
12x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
12x + x2 = -21

The x term is 12x.  Take half its coefficient (6).
Square it (36) and add it to both sides.

Add '36' to each side of the equation.
12x + 36 + x2 = -21 + 36

Reorder the terms:
36 + 12x + x2 = -21 + 36

Combine like terms: -21 + 36 = 15
36 + 12x + x2 = 15

Factor a perfect square on the left side:
(x + 6)(x + 6) = 15

Calculate the square root of the right side: 3.872983346

Break this problem into two subproblems by setting 
(x + 6) equal to 3.872983346 and -3.872983346.

Subproblem 1

x + 6 = 3.872983346 Simplifying x + 6 = 3.872983346 Reorder the terms: 6 + x = 3.872983346 Solving 6 + x = 3.872983346 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = 3.872983346 + -6 Combine like terms: 6 + -6 = 0 0 + x = 3.872983346 + -6 x = 3.872983346 + -6 Combine like terms: 3.872983346 + -6 = -2.127016654 x = -2.127016654 Simplifying x = -2.127016654

Subproblem 2

x + 6 = -3.872983346 Simplifying x + 6 = -3.872983346 Reorder the terms: 6 + x = -3.872983346 Solving 6 + x = -3.872983346 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-6' to each side of the equation. 6 + -6 + x = -3.872983346 + -6 Combine like terms: 6 + -6 = 0 0 + x = -3.872983346 + -6 x = -3.872983346 + -6 Combine like terms: -3.872983346 + -6 = -9.872983346 x = -9.872983346 Simplifying x = -9.872983346

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-2.127016654, -9.872983346}

See similar equations:

| -7*1= | | z(z-3)(2z+1)=0 | | -7*-1= | | 2x*2+4*2=3x*2+2x | | 2n^2+5n+7=0 | | 50x=300 | | 6x-5=2x-5x | | 2m+3m(m-8)=1 | | 3t^2+4t+21=0 | | 6-3-4=2+x | | 2x*2+8*2=3x*2+2x | | .05(.3m+35n)-.8(-.09n-22)= | | 2(x+3)+x=4(-3) | | -5-r=10 | | f(x)=x^2+6x+18 | | 8x+3(2-3x)=25 | | 194-2x=43x+19 | | 24x^2+24x=0 | | 27+(4x-30)+(3x-10)+x=360 | | 4(1)-5y=9 | | a^3+7a^2+12a+24= | | 6x^2-9x-105=0 | | 15=200 | | -3x+4y=21 | | -10x+6y=-2(3-y) | | 65-131=11(x-1) | | x-11=-3-20 | | -2x=-6y+9 | | 11x-10x=8x+5 | | x+3=-28+10 | | 4a^2+2.25a+1=0 | | (x+8)(x)(x-2)=96 |

Equations solver categories