5b^2-7b-42=

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Solution for 5b^2-7b-42= equation:


Simplifying
5b2 + -7b + -42 = 0

Reorder the terms:
-42 + -7b + 5b2 = 0

Solving
-42 + -7b + 5b2 = 0

Solving for variable 'b'.

Begin completing the square.  Divide all terms by
5 the coefficient of the squared term: 

Divide each side by '5'.
-8.4 + -1.4b + b2 = 0

Move the constant term to the right:

Add '8.4' to each side of the equation.
-8.4 + -1.4b + 8.4 + b2 = 0 + 8.4

Reorder the terms:
-8.4 + 8.4 + -1.4b + b2 = 0 + 8.4

Combine like terms: -8.4 + 8.4 = 0.0
0.0 + -1.4b + b2 = 0 + 8.4
-1.4b + b2 = 0 + 8.4

Combine like terms: 0 + 8.4 = 8.4
-1.4b + b2 = 8.4

The b term is -1.4b.  Take half its coefficient (-0.7).
Square it (0.49) and add it to both sides.

Add '0.49' to each side of the equation.
-1.4b + 0.49 + b2 = 8.4 + 0.49

Reorder the terms:
0.49 + -1.4b + b2 = 8.4 + 0.49

Combine like terms: 8.4 + 0.49 = 8.89
0.49 + -1.4b + b2 = 8.89

Factor a perfect square on the left side:
(b + -0.7)(b + -0.7) = 8.89

Calculate the square root of the right side: 2.981610303

Break this problem into two subproblems by setting 
(b + -0.7) equal to 2.981610303 and -2.981610303.

Subproblem 1

b + -0.7 = 2.981610303 Simplifying b + -0.7 = 2.981610303 Reorder the terms: -0.7 + b = 2.981610303 Solving -0.7 + b = 2.981610303 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + b = 2.981610303 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + b = 2.981610303 + 0.7 b = 2.981610303 + 0.7 Combine like terms: 2.981610303 + 0.7 = 3.681610303 b = 3.681610303 Simplifying b = 3.681610303

Subproblem 2

b + -0.7 = -2.981610303 Simplifying b + -0.7 = -2.981610303 Reorder the terms: -0.7 + b = -2.981610303 Solving -0.7 + b = -2.981610303 Solving for variable 'b'. Move all terms containing b to the left, all other terms to the right. Add '0.7' to each side of the equation. -0.7 + 0.7 + b = -2.981610303 + 0.7 Combine like terms: -0.7 + 0.7 = 0.0 0.0 + b = -2.981610303 + 0.7 b = -2.981610303 + 0.7 Combine like terms: -2.981610303 + 0.7 = -2.281610303 b = -2.281610303 Simplifying b = -2.281610303

Solution

The solution to the problem is based on the solutions from the subproblems. b = {3.681610303, -2.281610303}

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