4r^2-5r-21=0

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Solution for 4r^2-5r-21=0 equation:


Simplifying
4r2 + -5r + -21 = 0

Reorder the terms:
-21 + -5r + 4r2 = 0

Solving
-21 + -5r + 4r2 = 0

Solving for variable 'r'.

Factor a trinomial.
(-7 + -4r)(3 + -1r) = 0

Subproblem 1

Set the factor '(-7 + -4r)' equal to zero and attempt to solve: Simplifying -7 + -4r = 0 Solving -7 + -4r = 0 Move all terms containing r to the left, all other terms to the right. Add '7' to each side of the equation. -7 + 7 + -4r = 0 + 7 Combine like terms: -7 + 7 = 0 0 + -4r = 0 + 7 -4r = 0 + 7 Combine like terms: 0 + 7 = 7 -4r = 7 Divide each side by '-4'. r = -1.75 Simplifying r = -1.75

Subproblem 2

Set the factor '(3 + -1r)' equal to zero and attempt to solve: Simplifying 3 + -1r = 0 Solving 3 + -1r = 0 Move all terms containing r to the left, all other terms to the right. Add '-3' to each side of the equation. 3 + -3 + -1r = 0 + -3 Combine like terms: 3 + -3 = 0 0 + -1r = 0 + -3 -1r = 0 + -3 Combine like terms: 0 + -3 = -3 -1r = -3 Divide each side by '-1'. r = 3 Simplifying r = 3

Solution

r = {-1.75, 3}

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