How do you factor $3 x^{2} - 7 x - 20$ $3x^2 - 7x - 20$ ?

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Answer 1 · 2016-07-06T08:55:15

$(3 x + 5) (x - 4)$ $(3x +5)(x -4)$

$3 x^{2} - 7 x - 20$ $color(Blue)3x^2 color(purple)-color(green)7x color(red)-color(blue)20$

Find the factors of $3 and 20$ $color(blue)(3 and 20)$ which $(SUBTRACT)$ $color(red)"(SUBTRACT)"$ to give $7$ $color(green)7$ .

The signs will be $DIFFERENT$ $color(red)"DIFFERENT"$ , there must be more $negatives$ $color(purple)"negatives"$

Find the factors and try different combinations. Cross multiply and find the difference until you get 7.

$3 +5 \Rightarrow 1 \times + 5 +5$ $"3 +5 "rArr 1 xx+5" +5"$
$1 -4 \Rightarrow 3 \times - 4 -12$ $"1 -4 "rArr3 xx-4" -12"$
$- 7$ $" "-7$

$(3 x + 5) (x - 4)$ $(3x +5)(x -4)$

How do you factor 3x2−7x−20 3x^2 - 7x - 20?