-21=3r(r-9)-9

Simple and best practice solution for -21=3r(r-9)-9 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=3r(r-9)-9 equation:


Simplifying
-21 = 3r(r + -9) + -9

Reorder the terms:
-21 = 3r(-9 + r) + -9
-21 = (-9 * 3r + r * 3r) + -9
-21 = (-27r + 3r2) + -9

Reorder the terms:
-21 = -9 + -27r + 3r2

Solving
-21 = -9 + -27r + 3r2

Solving for variable 'r'.

Combine like terms: -21 + 9 = -12
-12 + 27r + -3r2 = -9 + -27r + 3r2 + 9 + 27r + -3r2

Reorder the terms:
-12 + 27r + -3r2 = -9 + 9 + -27r + 27r + 3r2 + -3r2

Combine like terms: -9 + 9 = 0
-12 + 27r + -3r2 = 0 + -27r + 27r + 3r2 + -3r2
-12 + 27r + -3r2 = -27r + 27r + 3r2 + -3r2

Combine like terms: -27r + 27r = 0
-12 + 27r + -3r2 = 0 + 3r2 + -3r2
-12 + 27r + -3r2 = 3r2 + -3r2

Combine like terms: 3r2 + -3r2 = 0
-12 + 27r + -3r2 = 0

Factor out the Greatest Common Factor (GCF), '3'.
3(-4 + 9r + -1r2) = 0

Ignore the factor 3.

Subproblem 1

Set the factor '(-4 + 9r + -1r2)' equal to zero and attempt to solve: Simplifying -4 + 9r + -1r2 = 0 Solving -4 + 9r + -1r2 = 0 Begin completing the square. Divide all terms by -1 the coefficient of the squared term: Divide each side by '-1'. 4 + -9r + r2 = 0 Move the constant term to the right: Add '-4' to each side of the equation. 4 + -9r + -4 + r2 = 0 + -4 Reorder the terms: 4 + -4 + -9r + r2 = 0 + -4 Combine like terms: 4 + -4 = 0 0 + -9r + r2 = 0 + -4 -9r + r2 = 0 + -4 Combine like terms: 0 + -4 = -4 -9r + r2 = -4 The r term is -9r. Take half its coefficient (-4.5). Square it (20.25) and add it to both sides. Add '20.25' to each side of the equation. -9r + 20.25 + r2 = -4 + 20.25 Reorder the terms: 20.25 + -9r + r2 = -4 + 20.25 Combine like terms: -4 + 20.25 = 16.25 20.25 + -9r + r2 = 16.25 Factor a perfect square on the left side: (r + -4.5)(r + -4.5) = 16.25 Calculate the square root of the right side: 4.031128874 Break this problem into two subproblems by setting (r + -4.5) equal to 4.031128874 and -4.031128874.

Subproblem 1

r + -4.5 = 4.031128874 Simplifying r + -4.5 = 4.031128874 Reorder the terms: -4.5 + r = 4.031128874 Solving -4.5 + r = 4.031128874 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + r = 4.031128874 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + r = 4.031128874 + 4.5 r = 4.031128874 + 4.5 Combine like terms: 4.031128874 + 4.5 = 8.531128874 r = 8.531128874 Simplifying r = 8.531128874

Subproblem 2

r + -4.5 = -4.031128874 Simplifying r + -4.5 = -4.031128874 Reorder the terms: -4.5 + r = -4.031128874 Solving -4.5 + r = -4.031128874 Solving for variable 'r'. Move all terms containing r to the left, all other terms to the right. Add '4.5' to each side of the equation. -4.5 + 4.5 + r = -4.031128874 + 4.5 Combine like terms: -4.5 + 4.5 = 0.0 0.0 + r = -4.031128874 + 4.5 r = -4.031128874 + 4.5 Combine like terms: -4.031128874 + 4.5 = 0.468871126 r = 0.468871126 Simplifying r = 0.468871126

Solution

The solution to the problem is based on the solutions from the subproblems. r = {8.531128874, 0.468871126}

Solution

r = {8.531128874, 0.468871126}

See similar equations:

| 487=512-n | | 7(1-5p)+8=15-5p | | 9m-4=-3+5+12m | | -21=3z-19 | | 8x^2-16x-18=0 | | 5(1-y)/2=-y | | 150m-75m+42750=45675-150m | | 2e^3x=5e^4x | | -2(1-7r)=38+6r | | x+15+10x-20+x+15= | | 60=(5x+10) | | 2y=4(8x-4) | | 0.18y+0.02(y+7000)=1540 | | y+2=6-y | | 26+5x=9x | | 7n-9=5n+7 | | 5n=30+8n | | 2(x*6)+2(6*5)+2(x*5)=30x | | -7.1+7.2= | | 8x^2-16-18=0 | | 3x-5(x-2)=-9+5x-23 | | 4x+1.6=8 | | 120=(5x+10) | | x-30+2x-120+.5x+15= | | 7c*2e= | | 0.59x+25=1.09x | | 2(x+3)=6x+30 | | (2/5)x+(4/5)=(-2/5) | | 4x^3+12x+4=0 | | 1.3x=-24 | | x^2+11x+45=-4x+1 | | 74=7x-53 |

Equations solver categories