x^2+20x+21=0

Simple and best practice solution for x^2+20x+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 x^2+20x+21=0 equation:


Simplifying
x2 + 20x + 21 = 0

Reorder the terms:
21 + 20x + x2 = 0

Solving
21 + 20x + x2 = 0

Solving for variable 'x'.

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + 20x + -21 + x2 = 0 + -21

Reorder the terms:
21 + -21 + 20x + x2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + 20x + x2 = 0 + -21
20x + x2 = 0 + -21

Combine like terms: 0 + -21 = -21
20x + x2 = -21

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 = -21 + 100

Reorder the terms:
100 + 20x + x2 = -21 + 100

Combine like terms: -21 + 100 = 79
100 + 20x + x2 = 79

Factor a perfect square on the left side:
(x + 10)(x + 10) = 79

Calculate the square root of the right side: 8.888194417

Break this problem into two subproblems by setting 
(x + 10) equal to 8.888194417 and -8.888194417.

Subproblem 1

x + 10 = 8.888194417 Simplifying x + 10 = 8.888194417 Reorder the terms: 10 + x = 8.888194417 Solving 10 + x = 8.888194417 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 = 8.888194417 + -10 Combine like terms: 10 + -10 = 0 0 + x = 8.888194417 + -10 x = 8.888194417 + -10 Combine like terms: 8.888194417 + -10 = -1.111805583 x = -1.111805583 Simplifying x = -1.111805583

Subproblem 2

x + 10 = -8.888194417 Simplifying x + 10 = -8.888194417 Reorder the terms: 10 + x = -8.888194417 Solving 10 + x = -8.888194417 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 = -8.888194417 + -10 Combine like terms: 10 + -10 = 0 0 + x = -8.888194417 + -10 x = -8.888194417 + -10 Combine like terms: -8.888194417 + -10 = -18.888194417 x = -18.888194417 Simplifying x = -18.888194417

Solution

The solution to the problem is based on the solutions from the subproblems. x = {-1.111805583, -18.888194417}

See similar equations:

| (y-3)(y-2)=0 | | -13d-21=-3(d+7)-10a | | 17x^2-9x=0 | | 7m^2=-63m | | xy+3y-8x-24=0 | | 2x-32=16 | | 4(5x-2)+6=2(2x-3)-6x | | 24y^2+13y-78=0 | | 2x+4(x-5)=7 | | 40x+8*1.5x=500 | | 4x^2-1x+3-3=0 | | 4x+5=-5 | | 9y=10x-90 | | 7a-5=2a+40 | | 9(5b-7)= | | 34-(-8)-42= | | 5w+2=2w+23 | | 6(3+5x)-1=197 | | 7y=5y^2+2 | | (x+5)(3x+1)=0 | | 2x^3+8x^2+12x-8=0 | | -4y=3y^2-7 | | -14+(-3)+7+(-6)= | | -9y=4y^2+5 | | -6y=4y^2-4 | | 0=x^3+3x^2-16x-48 | | 11x+5-7x+21x= | | 4r-16=-12+5r | | 7x-8=-17+8x | | (3v-4)(4v-6)=0 | | x^2-8x=x+18 | | -6(1+7k)+(1+6k)=-2 |

Equations solver categories