What are the solutions to the equation f^2-4f=21 ?

The solutions to the equation f^2-4f=21 are f=7,f=-3

Find the zeros of f^2-4f=21

The zeros of f^2-4f=21 are f=7,f=-3

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f^{2} - 4 f = 21

f = 7, f = - 3

Solution steps

f^{2} - 4 f = 21

Move

21

to the left side

f^{2} - 4 f - 21 = 0

Solve with the quadratic formula

f_{1, 2} = \frac{- ( - 4 ) \pm ( - 4 ) ^{2} - 4 \cdot 1 \cdot ( - 21 )}{2 \cdot 1}

(- 4)^{2} - 4 \cdot 1 \cdot (- 21) = 10

f_{1, 2} = \frac{- ( - 4 ) \pm 10}{2 \cdot 1}

Separate the solutions

f_{1} = \frac{- ( - 4 ) + 10}{2 \cdot 1}, f_{2} = \frac{- ( - 4 ) - 10}{2 \cdot 1}

f = \frac{- ( - 4 ) + 10}{2 \cdot 1} : 7

f = \frac{- ( - 4 ) - 10}{2 \cdot 1} : - 3

The solutions to the quadratic equation are:

f = 7, f = - 3

6 x^{2} - 2 = 7 x

2 x^{2} - 16 x + 16 = - 10 + 16

2.5 x^{2} + 25 x - 240 = 0

m^{2} - 12 m = 0

4 x^{2} - 13 x + 9 = 0

What are the solutions to the equation f^2-4f=21 ?
The solutions to the equation f^2-4f=21 are f=7,f=-3
Find the zeros of f^2-4f=21
The zeros of f^2-4f=21 are f=7,f=-3