k^2+72k+21=0

Simple and best practice solution for k^2+72k+21=0 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 k^2+72k+21=0 equation:


Simplifying
k2 + 72k + 21 = 0

Reorder the terms:
21 + 72k + k2 = 0

Solving
21 + 72k + k2 = 0

Solving for variable 'k'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 72k + -21 + k2 = 0 + -21

Reorder the terms:
21 + -21 + 72k + k2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 72k + k2 = 0 + -21
72k + k2 = 0 + -21

Combine like terms: 0 + -21 = -21
72k + k2 = -21

The k term is 72k.  Take half its coefficient (36).
Square it (1296) and add it to both sides.

Add '1296' to each side of the equation.
72k + 1296 + k2 = -21 + 1296

Reorder the terms:
1296 + 72k + k2 = -21 + 1296

Combine like terms: -21 + 1296 = 1275
1296 + 72k + k2 = 1275

Factor a perfect square on the left side:
(k + 36)(k + 36) = 1275

Calculate the square root of the right side: 35.707142143

Break this problem into two subproblems by setting 
(k + 36) equal to 35.707142143 and -35.707142143.

Subproblem 1

k + 36 = 35.707142143 Simplifying k + 36 = 35.707142143 Reorder the terms: 36 + k = 35.707142143 Solving 36 + k = 35.707142143 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-36' to each side of the equation. 36 + -36 + k = 35.707142143 + -36 Combine like terms: 36 + -36 = 0 0 + k = 35.707142143 + -36 k = 35.707142143 + -36 Combine like terms: 35.707142143 + -36 = -0.292857857 k = -0.292857857 Simplifying k = -0.292857857

Subproblem 2

k + 36 = -35.707142143 Simplifying k + 36 = -35.707142143 Reorder the terms: 36 + k = -35.707142143 Solving 36 + k = -35.707142143 Solving for variable 'k'. Move all terms containing k to the left, all other terms to the right. Add '-36' to each side of the equation. 36 + -36 + k = -35.707142143 + -36 Combine like terms: 36 + -36 = 0 0 + k = -35.707142143 + -36 k = -35.707142143 + -36 Combine like terms: -35.707142143 + -36 = -71.707142143 k = -71.707142143 Simplifying k = -71.707142143

Solution

The solution to the problem is based on the solutions from the subproblems. k = {-0.292857857, -71.707142143}

See similar equations:

| -[7z-(17z+10)]=10+(9z+7) | | 3r+4-3+4s=7 | | (16•3^x)^1/4 | | 0.09xX=114.19 | | 7(2+x)=90 | | Tanx=-1.2 | | 2y=17+y | | 9x-4(2+4x-6)=4 | | d/6=36 | | A^3+2=3 | | 20x^3+3x^2-2x= | | (n/2)-410 | | n-25=41 | | 21k^2+72k+0=0 | | (1/4*5/4) | | g+45=56 | | 1/4***5/4 | | 0.09xX=119.49 | | 3p-10-8p=30 | | 21k^2+72k=0 | | 1/4*5/4 | | 2/3-5/6x | | r^15=0.15 | | 1/2x-34 | | 2/35/6x | | 2d^2-9d+9=0 | | t-54=85 | | 6w+18=3 | | 2-2t=15-7t+8 | | 1x+20=45 | | 2-.4(x-3)=.1(9x-3) | | 1+r^15=0.15 |

Equations solver categories