p^2-15p=-21

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Solution for p^2-15p=-21 equation:


Simplifying
p2 + -15p = -21

Reorder the terms:
-15p + p2 = -21

Solving
-15p + p2 = -21

Solving for variable 'p'.

Reorder the terms:
21 + -15p + p2 = -21 + 21

Combine like terms: -21 + 21 = 0
21 + -15p + p2 = 0

Begin completing the square.

Move the constant term to the right:

Add '-21' to each side of the equation.
21 + -15p + -21 + p2 = 0 + -21

Reorder the terms:
21 + -21 + -15p + p2 = 0 + -21

Combine like terms: 21 + -21 = 0
0 + -15p + p2 = 0 + -21
-15p + p2 = 0 + -21

Combine like terms: 0 + -21 = -21
-15p + p2 = -21

The p term is -15p.  Take half its coefficient (-7.5).
Square it (56.25) and add it to both sides.

Add '56.25' to each side of the equation.
-15p + 56.25 + p2 = -21 + 56.25

Reorder the terms:
56.25 + -15p + p2 = -21 + 56.25

Combine like terms: -21 + 56.25 = 35.25
56.25 + -15p + p2 = 35.25

Factor a perfect square on the left side:
(p + -7.5)(p + -7.5) = 35.25

Calculate the square root of the right side: 5.937171044

Break this problem into two subproblems by setting 
(p + -7.5) equal to 5.937171044 and -5.937171044.

Subproblem 1

p + -7.5 = 5.937171044 Simplifying p + -7.5 = 5.937171044 Reorder the terms: -7.5 + p = 5.937171044 Solving -7.5 + p = 5.937171044 Solving for variable 'p'. Move all terms containing p to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + p = 5.937171044 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + p = 5.937171044 + 7.5 p = 5.937171044 + 7.5 Combine like terms: 5.937171044 + 7.5 = 13.437171044 p = 13.437171044 Simplifying p = 13.437171044

Subproblem 2

p + -7.5 = -5.937171044 Simplifying p + -7.5 = -5.937171044 Reorder the terms: -7.5 + p = -5.937171044 Solving -7.5 + p = -5.937171044 Solving for variable 'p'. Move all terms containing p to the left, all other terms to the right. Add '7.5' to each side of the equation. -7.5 + 7.5 + p = -5.937171044 + 7.5 Combine like terms: -7.5 + 7.5 = 0.0 0.0 + p = -5.937171044 + 7.5 p = -5.937171044 + 7.5 Combine like terms: -5.937171044 + 7.5 = 1.562828956 p = 1.562828956 Simplifying p = 1.562828956

Solution

The solution to the problem is based on the solutions from the subproblems. p = {13.437171044, 1.562828956}

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