0=x^2+20x-81

Simple and best practice solution for 0=x^2+20x-81 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 0=x^2+20x-81 equation:


Simplifying
0 = x2 + 20x + -81

Reorder the terms:
0 = -81 + 20x + x2

Solving
0 = -81 + 20x + x2

Solving for variable 'x'.

Combine like terms: 0 + 81 = 81
81 + -20x + -1x2 = -81 + 20x + x2 + 81 + -20x + -1x2

Reorder the terms:
81 + -20x + -1x2 = -81 + 81 + 20x + -20x + x2 + -1x2

Combine like terms: -81 + 81 = 0
81 + -20x + -1x2 = 0 + 20x + -20x + x2 + -1x2
81 + -20x + -1x2 = 20x + -20x + x2 + -1x2

Combine like terms: 20x + -20x = 0
81 + -20x + -1x2 = 0 + x2 + -1x2
81 + -20x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
81 + -20x + -1x2 = 0

Begin completing the square.  Divide all terms by
-1 the coefficient of the squared term: 

Divide each side by '-1'.
-81 + 20x + x2 = 0

Move the constant term to the right:

Add '81' to each side of the equation.
-81 + 20x + 81 + x2 = 0 + 81

Reorder the terms:
-81 + 81 + 20x + x2 = 0 + 81

Combine like terms: -81 + 81 = 0
0 + 20x + x2 = 0 + 81
20x + x2 = 0 + 81

Combine like terms: 0 + 81 = 81
20x + x2 = 81

The x term is 20x.  Take half its coefficient (10).
Square it (100) and add it to both sides.

Add '100' to each side of the equation.
20x + 100 + x2 = 81 + 100

Reorder the terms:
100 + 20x + x2 = 81 + 100

Combine like terms: 81 + 100 = 181
100 + 20x + x2 = 181

Factor a perfect square on the left side:
(x + 10)(x + 10) = 181

Calculate the square root of the right side: 13.453624047

Break this problem into two subproblems by setting 
(x + 10) equal to 13.453624047 and -13.453624047.

Subproblem 1

x + 10 = 13.453624047 Simplifying x + 10 = 13.453624047 Reorder the terms: 10 + x = 13.453624047 Solving 10 + x = 13.453624047 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10' to each side of the equation. 10 + -10 + x = 13.453624047 + -10 Combine like terms: 10 + -10 = 0 0 + x = 13.453624047 + -10 x = 13.453624047 + -10 Combine like terms: 13.453624047 + -10 = 3.453624047 x = 3.453624047 Simplifying x = 3.453624047

Subproblem 2

x + 10 = -13.453624047 Simplifying x + 10 = -13.453624047 Reorder the terms: 10 + x = -13.453624047 Solving 10 + x = -13.453624047 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-10' to each side of the equation. 10 + -10 + x = -13.453624047 + -10 Combine like terms: 10 + -10 = 0 0 + x = -13.453624047 + -10 x = -13.453624047 + -10 Combine like terms: -13.453624047 + -10 = -23.453624047 x = -23.453624047 Simplifying x = -23.453624047

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.453624047, -23.453624047}

See similar equations:

| (12-3x/20x)/(16-x^2/5) | | x^2-2a(x-1)-1=0 | | 3a(5a-2b)= | | 81-90x+25x^2=x^2 | | .5d^2-1.25d-3=0 | | x^4+3x^3-3x+9=0 | | x+0.0875=7 | | 3/4x2-13=14 | | x+0.875x=7 | | H=-16t^2-26t+140 | | x^3+50x^2+800x+4000=0 | | 2x-8=11x+21 | | 17x=-10x | | 35=7-x | | 7.2x=1.8*0.6 | | (-5/3)-(1/-2) | | y^3-10y+27=0 | | 1/2x+x=4-2 | | f(2)=4x+3 | | 3x-2x=8+12 | | 17-7=5 | | 3z/-8=-3 | | 4x^2=8x+45 | | 5x-4x=15 | | 23-3m=5m-7 | | 2(x^2-4)-x^6+3(2x+3)=5x | | 4=b/13 | | Y=2x^2-18x | | (2x-5)(7-x)=0 | | 8x-30=3 | | x+2y-3+m=0 | | 4x^2+52x=120 |

Equations solver categories