What are the solutions to the equation 2r^3+7r^2-4r-21=0 ?

The solutions to the equation 2r^3+7r^2-4r-21=0 are r=-3,r=(-1+sqrt(57))/4 ,r=(-1-sqrt(57))/4

Find the zeros of 2r^3+7r^2-4r-21=0

The zeros of 2r^3+7r^2-4r-21=0 are r=-3,r=(-1+sqrt(57))/4 ,r=(-1-sqrt(57))/4

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2 r^{3} + 7 r^{2} - 4 r - 21 = 0

r = - 3, r = \frac{- 1 + 57}{4}, r = \frac{- 1 - 57}{4}

Decimal Notation

r = - 3, r = 1.63745 \dots, r = - 2.13745 \dots

Solution steps

2 r^{3} + 7 r^{2} - 4 r - 21 = 0

Factor

2 r^{3} + 7 r^{2} - 4 r - 21 : (r + 3) (2 r^{2} + r - 7)

(r + 3) (2 r^{2} + r - 7) = 0

Using the Zero Factor Principle:

ab = 0

then

a = 0

b = 0

r + 3 = 0 or 2 r^{2} + r - 7 = 0

Solve

r + 3 = 0 : r = - 3

Solve

2 r^{2} + r - 7 = 0 : r = \frac{- 1 + 57}{4}, r = \frac{- 1 - 57}{4}

The solutions are

r = - 3, r = \frac{- 1 + 57}{4}, r = \frac{- 1 - 57}{4}

(1 + 0.0239193)^{1} = (1 + x)^{3}

8 x^{3} - 12 x^{2} + 6 x - 65 = 0

2 x^{1} + x^{2} - x^{3} + x^{4} = - 2

x^{3} = 5 x^{2} - 6 x

(3 p + 7) (3 p - 7) (p + 8) = 0

What are the solutions to the equation 2r^3+7r^2-4r-21=0 ?
The solutions to the equation 2r^3+7r^2-4r-21=0 are r=-3,r=(-1+sqrt(57))/4 ,r=(-1-sqrt(57))/4
Find the zeros of 2r^3+7r^2-4r-21=0
The zeros of 2r^3+7r^2-4r-21=0 are r=-3,r=(-1+sqrt(57))/4 ,r=(-1-sqrt(57))/4