(x+8)(x-2)=21

Simple and best practice solution for (x+8)(x-2)=21 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+8)(x-2)=21 equation:


Simplifying
(x + 8)(x + -2) = 21

Reorder the terms:
(8 + x)(x + -2) = 21

Reorder the terms:
(8 + x)(-2 + x) = 21

Multiply (8 + x) * (-2 + x)
(8(-2 + x) + x(-2 + x)) = 21
((-2 * 8 + x * 8) + x(-2 + x)) = 21
((-16 + 8x) + x(-2 + x)) = 21
(-16 + 8x + (-2 * x + x * x)) = 21
(-16 + 8x + (-2x + x2)) = 21

Combine like terms: 8x + -2x = 6x
(-16 + 6x + x2) = 21

Solving
-16 + 6x + x2 = 21

Solving for variable 'x'.

Reorder the terms:
-16 + -21 + 6x + x2 = 21 + -21

Combine like terms: -16 + -21 = -37
-37 + 6x + x2 = 21 + -21

Combine like terms: 21 + -21 = 0
-37 + 6x + x2 = 0

Begin completing the square.

Move the constant term to the right:

Add '37' to each side of the equation.
-37 + 6x + 37 + x2 = 0 + 37

Reorder the terms:
-37 + 37 + 6x + x2 = 0 + 37

Combine like terms: -37 + 37 = 0
0 + 6x + x2 = 0 + 37
6x + x2 = 0 + 37

Combine like terms: 0 + 37 = 37
6x + x2 = 37

The x term is 6x.  Take half its coefficient (3).
Square it (9) and add it to both sides.

Add '9' to each side of the equation.
6x + 9 + x2 = 37 + 9

Reorder the terms:
9 + 6x + x2 = 37 + 9

Combine like terms: 37 + 9 = 46
9 + 6x + x2 = 46

Factor a perfect square on the left side:
(x + 3)(x + 3) = 46

Calculate the square root of the right side: 6.782329983

Break this problem into two subproblems by setting 
(x + 3) equal to 6.782329983 and -6.782329983.

Subproblem 1

x + 3 = 6.782329983 Simplifying x + 3 = 6.782329983 Reorder the terms: 3 + x = 6.782329983 Solving 3 + x = 6.782329983 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + x = 6.782329983 + -3 Combine like terms: 3 + -3 = 0 0 + x = 6.782329983 + -3 x = 6.782329983 + -3 Combine like terms: 6.782329983 + -3 = 3.782329983 x = 3.782329983 Simplifying x = 3.782329983

Subproblem 2

x + 3 = -6.782329983 Simplifying x + 3 = -6.782329983 Reorder the terms: 3 + x = -6.782329983 Solving 3 + x = -6.782329983 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + x = -6.782329983 + -3 Combine like terms: 3 + -3 = 0 0 + x = -6.782329983 + -3 x = -6.782329983 + -3 Combine like terms: -6.782329983 + -3 = -9.782329983 x = -9.782329983 Simplifying x = -9.782329983

Solution

The solution to the problem is based on the solutions from the subproblems. x = {3.782329983, -9.782329983}

See similar equations:

| X^4=10 | | 3x^2-18x+2=16 | | -15x-3x=10x+18 | | 7/x=x/63 | | 3x^2-13x-28=0 | | 7/x=x/7 | | 2x^2-4x=10 | | 5x+15/18 | | x^2-10x+25=3a | | 13x+1=11x | | f(x)=-x^4+1 | | f(x)=x^4-6x^3+14x^2-14x+5 | | 3x^2-13x-17=0 | | 22=2y+2 | | 0.60=-x+1 | | -6x-3x+5x=12 | | 0.4y+2*0=1.2 | | 0.4y+2*-3=1.2 | | 1.50+2x=6.50 | | 0.25y-2*0=9 | | (3x+1)(x-3)=(2+3)(x+5) | | 0.25y-3*-2=9 | | 1/4y-3*-2=9 | | y=7/3x+1/3 | | 0.25x+6=12 | | 12*1+3y=15 | | 5x+(-10)=-20 | | 3(5x+3)=36 | | 4x-8=9x+4 | | c=15(13n+8) | | -7-(-9)+1x(-1)= | | 3x-18000=x |

Equations solver categories