21=x^2-4x

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


Simplifying
21 = x2 + -4x

Reorder the terms:
21 = -4x + x2

Solving
21 = -4x + x2

Solving for variable 'x'.

Reorder the terms:
21 + 4x + -1x2 = -4x + 4x + x2 + -1x2

Combine like terms: -4x + 4x = 0
21 + 4x + -1x2 = 0 + x2 + -1x2
21 + 4x + -1x2 = x2 + -1x2

Combine like terms: x2 + -1x2 = 0
21 + 4x + -1x2 = 0

Factor a trinomial.
(7 + -1x)(3 + x) = 0

Subproblem 1

Set the factor '(7 + -1x)' equal to zero and attempt to solve: Simplifying 7 + -1x = 0 Solving 7 + -1x = 0 Move all terms containing x to the left, all other terms to the right. Add '-7' to each side of the equation. 7 + -7 + -1x = 0 + -7 Combine like terms: 7 + -7 = 0 0 + -1x = 0 + -7 -1x = 0 + -7 Combine like terms: 0 + -7 = -7 -1x = -7 Divide each side by '-1'. x = 7 Simplifying x = 7

Subproblem 2

Set the factor '(3 + x)' equal to zero and attempt to solve: Simplifying 3 + x = 0 Solving 3 + x = 0 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 = 0 + -3 Combine like terms: 3 + -3 = 0 0 + x = 0 + -3 x = 0 + -3 Combine like terms: 0 + -3 = -3 x = -3 Simplifying x = -3

Solution

x = {7, -3}

See similar equations:

| 13-(x+7)=8x-3 | | 7x+4=4x-8 | | 7x+8=4x+20 | | 0=6v+5-v | | 4y+(-19x)-8y+2y= | | 2w+8=4w-8 | | -y^2-9y^2+3y^2= | | 8x^2-2x-28=0 | | 3x+12=5x-10 | | 0+(-1.6)+2.4=-1.6+2.4 | | x^2+8x-1=19 | | (5c+6)(5c-6)= | | q^2+1= | | -2y+8=-2(2y+4) | | 20y^2-25y+5= | | (4v-1)(5v-3)= | | x^2+2x-7=17 | | 4(x-2)-1=-7 | | 5-2a=5a+2 | | 8z-9=z+9 | | 24x^2-82x-63=0 | | x^2-11xy+24y^2= | | f(75)=0.81x+168.3 | | f(-2)=-2-9 | | 5z+10=6z-6 | | 4z+16=6z-6 | | 4y+5=-1 | | 4z+16=5z+10 | | 4y+5=1 | | x-(2x-5)=3x-8 | | w+8=2w-1 | | 1.5x+1=4x |

Equations solver categories