21=x*[x+2]

Simple and best practice solution for 21=x*[x+2] 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 21=x*[x+2] equation:


Simplifying
21 = x[x + 2]

Reorder the terms:
21 = x[2 + x]
21 = [2 * x + x * x]
21 = [2x + x2]

Solving
21 = 2x + x2

Solving for variable 'x'.

Reorder the terms:
21 + -2x + -1x2 = 2x + -2x + x2 + -1x2

Combine like terms: 2x + -2x = 0
21 + -2x + -1x2 = 0 + x2 + -1x2
21 + -2x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
21 + -2x + -1x2 = 0

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

Divide each side by '-1'.
-21 + 2x + x2 = 0

Move the constant term to the right:

Add '21' to each side of the equation.
-21 + 2x + 21 + x2 = 0 + 21

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

Combine like terms: -21 + 21 = 0
0 + 2x + x2 = 0 + 21
2x + x2 = 0 + 21

Combine like terms: 0 + 21 = 21
2x + x2 = 21

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 = 21 + 1

Reorder the terms:
1 + 2x + x2 = 21 + 1

Combine like terms: 21 + 1 = 22
1 + 2x + x2 = 22

Factor a perfect square on the left side:
(x + 1)(x + 1) = 22

Calculate the square root of the right side: 4.69041576

Break this problem into two subproblems by setting 
(x + 1) equal to 4.69041576 and -4.69041576.

Subproblem 1

x + 1 = 4.69041576 Simplifying x + 1 = 4.69041576 Reorder the terms: 1 + x = 4.69041576 Solving 1 + x = 4.69041576 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 = 4.69041576 + -1 Combine like terms: 1 + -1 = 0 0 + x = 4.69041576 + -1 x = 4.69041576 + -1 Combine like terms: 4.69041576 + -1 = 3.69041576 x = 3.69041576 Simplifying x = 3.69041576

Subproblem 2

x + 1 = -4.69041576 Simplifying x + 1 = -4.69041576 Reorder the terms: 1 + x = -4.69041576 Solving 1 + x = -4.69041576 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 = -4.69041576 + -1 Combine like terms: 1 + -1 = 0 0 + x = -4.69041576 + -1 x = -4.69041576 + -1 Combine like terms: -4.69041576 + -1 = -5.69041576 x = -5.69041576 Simplifying x = -5.69041576

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.69041576, -5.69041576}

See similar equations:

| 9b-3v-(8+2v)= | | w-2w+3=-2 | | 2x^5-8x^3=6x^4 | | 3(-x-1)+1=-3(3x-2) | | 3(-x-1)+1=-33(3x-2) | | 3x+9-ax-3a= | | 14y-6(y-2)=4(y-1) | | 6-n=2n | | y*y=260 | | 100=120+x^2-200-11x | | (2x+1)(8x+3)=0 | | x*x=260 | | 7st-14s^2t^2+21t^2= | | x+(x*.15)=375 | | 7x-10=10x-16 | | 7n-9=4n | | 2x-7=2x-6 | | 3y-4/5=-2/3y-2/5 | | x=6/7/2/3 | | 5x+2=2x+22 | | x+(x*.15x)=375 | | 8(j-4)=(4j-16) | | X+4(x+4+3x)=8(9+19) | | x^3-8x^2+x+42=0 | | 3j^3+21j^2+30j=0 | | X^2+10x-36=0 | | 3(x-0.2)-2(x+1.4)=5.4 | | 6+2(3j-12)=4(1+j) | | (10x-12x^2-7x^4)-(-4x^2-1+12x)= | | 5/√2-7 | | (4b)x=8xwhatisb | | 5x^2=3x+50 |

Equations solver categories