2x^2+4x-21=0

Simple and best practice solution for 2x^2+4x-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 2x^2+4x-21=0 equation:


Simplifying
2x2 + 4x + -21 = 0

Reorder the terms:
-21 + 4x + 2x2 = 0

Solving
-21 + 4x + 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'.
-10.5 + 2x + x2 = 0

Move the constant term to the right:

Add '10.5' to each side of the equation.
-10.5 + 2x + 10.5 + x2 = 0 + 10.5

Reorder the terms:
-10.5 + 10.5 + 2x + x2 = 0 + 10.5

Combine like terms: -10.5 + 10.5 = 0.0
0.0 + 2x + x2 = 0 + 10.5
2x + x2 = 0 + 10.5

Combine like terms: 0 + 10.5 = 10.5
2x + x2 = 10.5

The x term is 2x.  Take half its coefficient (1).
Square it (1) and add it to both sides.

Add '1' to each side of the equation.
2x + 1 + x2 = 10.5 + 1

Reorder the terms:
1 + 2x + x2 = 10.5 + 1

Combine like terms: 10.5 + 1 = 11.5
1 + 2x + x2 = 11.5

Factor a perfect square on the left side:
(x + 1)(x + 1) = 11.5

Calculate the square root of the right side: 3.391164992

Break this problem into two subproblems by setting 
(x + 1) equal to 3.391164992 and -3.391164992.

Subproblem 1

x + 1 = 3.391164992 Simplifying x + 1 = 3.391164992 Reorder the terms: 1 + x = 3.391164992 Solving 1 + x = 3.391164992 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = 3.391164992 + -1 Combine like terms: 1 + -1 = 0 0 + x = 3.391164992 + -1 x = 3.391164992 + -1 Combine like terms: 3.391164992 + -1 = 2.391164992 x = 2.391164992 Simplifying x = 2.391164992

Subproblem 2

x + 1 = -3.391164992 Simplifying x + 1 = -3.391164992 Reorder the terms: 1 + x = -3.391164992 Solving 1 + x = -3.391164992 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-1' to each side of the equation. 1 + -1 + x = -3.391164992 + -1 Combine like terms: 1 + -1 = 0 0 + x = -3.391164992 + -1 x = -3.391164992 + -1 Combine like terms: -3.391164992 + -1 = -4.391164992 x = -4.391164992 Simplifying x = -4.391164992

Solution

The solution to the problem is based on the solutions from the subproblems. x = {2.391164992, -4.391164992}

See similar equations:

| 9x+1=10x-5 | | 7w^2+4w-3w^2= | | 2xy^3-10x= | | 4.5*35= | | (5y+6)-(3+4y)=10 | | 35x^3y^4-60x^4y= | | =6+3(p-2) | | -2x^2+7x-60=0 | | 40=x+11(11) | | 3n+15=127-n | | 48x^2=24-84x | | x+0.95=-3.6 | | 14x^2-101x-30=0 | | 6x+18=-30 | | 25p^3+40p^2=0 | | 48x^2+125x-4=4 | | 2(10+0.5x)*3.14=94.2 | | x(5x-2)=0 | | 0=x^2-9x+20 | | 4.0x+2.7-1.6x=4.6x+2.7 | | x=x^2-9x+20 | | a^3-16a^2+28a=0 | | 3.0x+2.7-1.6x=4.6x+2.7 | | 2g^2-4g-48=0 | | 1.4x^2+x-2=0 | | 3x+15= | | 3x^2+9x+6= | | 2(8.5+x)*3.14=109.9 | | 46.2*10-2= | | 8-h=h+5 | | 4x^2-72=24x | | 8x+2y=4 |

Equations solver categories