2x^2+21x-8.1=0

Simple and best practice solution for 2x^2+21x-8.1=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 2x^2+21x-8.1=0 equation:


Simplifying
2x2 + 21x + -8.1 = 0

Reorder the terms:
-8.1 + 21x + 2x2 = 0

Solving
-8.1 + 21x + 2x2 = 0

Solving for variable 'x'.

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

Divide each side by '2'.
-4.05 + 10.5x + x2 = 0

Move the constant term to the right:

Add '4.05' to each side of the equation.
-4.05 + 10.5x + 4.05 + x2 = 0 + 4.05

Reorder the terms:
-4.05 + 4.05 + 10.5x + x2 = 0 + 4.05

Combine like terms: -4.05 + 4.05 = 0.00
0.00 + 10.5x + x2 = 0 + 4.05
10.5x + x2 = 0 + 4.05

Combine like terms: 0 + 4.05 = 4.05
10.5x + x2 = 4.05

The x term is 10.5x.  Take half its coefficient (5.25).
Square it (27.5625) and add it to both sides.

Add '27.5625' to each side of the equation.
10.5x + 27.5625 + x2 = 4.05 + 27.5625

Reorder the terms:
27.5625 + 10.5x + x2 = 4.05 + 27.5625

Combine like terms: 4.05 + 27.5625 = 31.6125
27.5625 + 10.5x + x2 = 31.6125

Factor a perfect square on the left side:
(x + 5.25)(x + 5.25) = 31.6125

Calculate the square root of the right side: 5.622499444

Break this problem into two subproblems by setting 
(x + 5.25) equal to 5.622499444 and -5.622499444.

Subproblem 1

x + 5.25 = 5.622499444 Simplifying x + 5.25 = 5.622499444 Reorder the terms: 5.25 + x = 5.622499444 Solving 5.25 + x = 5.622499444 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-5.25' to each side of the equation. 5.25 + -5.25 + x = 5.622499444 + -5.25 Combine like terms: 5.25 + -5.25 = 0.00 0.00 + x = 5.622499444 + -5.25 x = 5.622499444 + -5.25 Combine like terms: 5.622499444 + -5.25 = 0.372499444 x = 0.372499444 Simplifying x = 0.372499444

Subproblem 2

x + 5.25 = -5.622499444 Simplifying x + 5.25 = -5.622499444 Reorder the terms: 5.25 + x = -5.622499444 Solving 5.25 + x = -5.622499444 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-5.25' to each side of the equation. 5.25 + -5.25 + x = -5.622499444 + -5.25 Combine like terms: 5.25 + -5.25 = 0.00 0.00 + x = -5.622499444 + -5.25 x = -5.622499444 + -5.25 Combine like terms: -5.622499444 + -5.25 = -10.872499444 x = -10.872499444 Simplifying x = -10.872499444

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.372499444, -10.872499444}

See similar equations:

| x+10=x+15 | | 12+2n/2=4+6n/2 | | 35-r=10 | | 2x+9=8x+8-x | | 15m^2-21n+9= | | x^2-14x+49=53 | | z/17=-18 | | 9-0.25x=.75x+4 | | x/4+10=30 | | 2t+6t=40 | | 6x+30/4=2x-2 | | 3+n= | | 12+2n=4+6n | | y=8x-x^2+20 | | 3n+4=5(n+2)-5n | | 84=-7(k-4) | | -3x+10=5 | | x-2(x+2)=2 | | 2n=78 | | 3+9m-2=9m+11-2m | | 3u+3=3u+6 | | -5(3x+4)+(16x-6)=0 | | s=V/p | | 5-(x+1)=4-5x | | 1/2x-3=21 | | 2=8x-23 | | 12z-14z=8 | | 35=5(x+3) | | X^3-6x^2-9x=-54 | | 12x+13y=12 | | 6a^2+5ab-4b^2=0 | | 2x+5(x-1)=-26 |

Equations solver categories