r^2-13=8r

Simple and best practice solution for r^2-13=8r 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 r^2-13=8r equation:


Simplifying
r2 + -13 = 8r

Reorder the terms:
-13 + r2 = 8r

Solving
-13 + r2 = 8r

Solving for variable 'r'.

Reorder the terms:
-13 + -8r + r2 = 8r + -8r

Combine like terms: 8r + -8r = 0
-13 + -8r + r2 = 0

Begin completing the square.

Move the constant term to the right:

Add '13' to each side of the equation.
-13 + -8r + 13 + r2 = 0 + 13

Reorder the terms:
-13 + 13 + -8r + r2 = 0 + 13

Combine like terms: -13 + 13 = 0
0 + -8r + r2 = 0 + 13
-8r + r2 = 0 + 13

Combine like terms: 0 + 13 = 13
-8r + r2 = 13

The r term is -8r.  Take half its coefficient (-4).
Square it (16) and add it to both sides.

Add '16' to each side of the equation.
-8r + 16 + r2 = 13 + 16

Reorder the terms:
16 + -8r + r2 = 13 + 16

Combine like terms: 13 + 16 = 29
16 + -8r + r2 = 29

Factor a perfect square on the left side:
(r + -4)(r + -4) = 29

Calculate the square root of the right side: 5.385164807

Break this problem into two subproblems by setting 
(r + -4) equal to 5.385164807 and -5.385164807.

Subproblem 1

r + -4 = 5.385164807 Simplifying r + -4 = 5.385164807 Reorder the terms: -4 + r = 5.385164807 Solving -4 + r = 5.385164807 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + r = 5.385164807 + 4 Combine like terms: -4 + 4 = 0 0 + r = 5.385164807 + 4 r = 5.385164807 + 4 Combine like terms: 5.385164807 + 4 = 9.385164807 r = 9.385164807 Simplifying r = 9.385164807

Subproblem 2

r + -4 = -5.385164807 Simplifying r + -4 = -5.385164807 Reorder the terms: -4 + r = -5.385164807 Solving -4 + r = -5.385164807 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4' to each side of the equation. -4 + 4 + r = -5.385164807 + 4 Combine like terms: -4 + 4 = 0 0 + r = -5.385164807 + 4 r = -5.385164807 + 4 Combine like terms: -5.385164807 + 4 = -1.385164807 r = -1.385164807 Simplifying r = -1.385164807

Solution

The solution to the problem is based on the solutions from the subproblems. r = {9.385164807, -1.385164807}

See similar equations:

| 4x^2-18=11x | | (x+y^3)dx+(3y^5-3y^2x)dy=0 | | I=(40000)(0.067)(4) | | am-b=c | | 6x^2-9x=7 | | A=-16+5n | | p^2+7=-8p | | -8z=26 | | 740/962=n/100 | | x+x-1+10=180 | | 5p+2=37 | | y^2-5/3*y-25/36=0 | | 3X^(2/3)=48 | | 2m^2=99-7m | | ((x^2)-x-12)/(x-3) | | 3n^2=-12-12n | | -11z+2=-10x | | 3X^2/3=48 | | 2y^2-11y-1=0 | | 3(3n-2)=39 | | 19=-3x+25 | | a^2-60=11a | | y^2-(5/3)y-(25/36)=0 | | 8t=20 | | Y=0.15x-8 | | -s=-5 | | X/4-3=17 | | 8x+7=y | | -14=11r-4r | | 3k^2=19+5k | | 1=0.1x-0.6x-4 | | f(x)=-5x^2+3x+7 |

Equations solver categories