x^2+6x=21

Simple and best practice solution for x^2+6x=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+6x=21 equation:


Simplifying
x2 + 6x = 21

Reorder the terms:
6x + x2 = 21

Solving
6x + x2 = 21

Solving for variable 'x'.

Reorder the terms:
-21 + 6x + x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-21 + 6x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + 6x + 21 + x2 = 0 + 21

Reorder the terms:
-21 + 21 + 6x + x2 = 0 + 21

Combine like terms: -21 + 21 = 0
0 + 6x + x2 = 0 + 21
6x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
6x + x2 = 21

The x term is 6x.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6x + 9 + x2 = 21 + 9

Reorder the terms:
9 + 6x + x2 = 21 + 9

Combine like terms: 21 + 9 = 30
9 + 6x + x2 = 30

Factor a perfect square on the left side:
(x + 3)(x + 3) = 30

Calculate the square root of the right side: 5.477225575

Break this problem into two subproblems by setting 
(x + 3) equal to 5.477225575 and -5.477225575.

Subproblem 1

x + 3 = 5.477225575 Simplifying x + 3 = 5.477225575 Reorder the terms: 3 + x = 5.477225575 Solving 3 + x = 5.477225575 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + x = 5.477225575 + -3 Combine like terms: 3 + -3 = 0 0 + x = 5.477225575 + -3 x = 5.477225575 + -3 Combine like terms: 5.477225575 + -3 = 2.477225575 x = 2.477225575 Simplifying x = 2.477225575

Subproblem 2

x + 3 = -5.477225575 Simplifying x + 3 = -5.477225575 Reorder the terms: 3 + x = -5.477225575 Solving 3 + x = -5.477225575 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + x = -5.477225575 + -3 Combine like terms: 3 + -3 = 0 0 + x = -5.477225575 + -3 x = -5.477225575 + -3 Combine like terms: -5.477225575 + -3 = -8.477225575 x = -8.477225575 Simplifying x = -8.477225575

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.477225575, -8.477225575}

See similar equations:

| 6r^2-30=-24r | | 7-1/2k=32 | | 12+6x=3y | | 4x-Ay=15 | | 3p-5=6 | | 20x+25y=115 | | 7x+(5-4x)=3x | | 8=224-9w | | 1639.9997=1/3*691.69*h | | -3x+y=-5+2x | | y/4=20 | | (x+6y)(5x-y)= | | 4m^2-5m=0 | | 6w+34=41 | | r/7=15 | | 3x-21=2x-6 | | 5x+-5x^2=-10 | | 6w+38=41 | | 63x^2-42x+60=0 | | 38-8y=4 | | P(x)=x^4+3x^3+2x^2-1 | | 9x+4=3-(6x-5) | | 4(12)+2=50 | | 1/5(5x23)=12 | | 5x-5+2x=9x+23-6x | | V=(bh/3) | | 2x^4-10x^2+13=0 | | 2=4+14 | | y=-3c-2 | | 5x+4x=3+8x+1 | | 7x+4=7-(6x-5) | | 8p+3=29 |

Equations solver categories