What is factor r^2-4r-21 ?

The solution to factor r^2-4r-21 is (r+3)(r-7)

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factor r^2-4r-21

factor

r^{2} - 4 r - 21

(r + 3) (r - 7)

Solution steps

r^{2} - 4 r - 21

Break the expression into groups

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

Factor out

r

from

r^{2} + 3 r : r (r + 3)

Factor out

- 7

from

- 7 r - 21 : - 7 (r + 3)

= r (r + 3) - 7 (r + 3)

Factor out common term

r + 3

= (r + 3) (r - 7)

\frac{1}{2 6}

16 k^{2} - 84 k + 104 > 0

8 y^{3} - x^{3}

2 x + 1 \leq 7

5 x^{2} = 100