How do you multiply $(x+4)(x^2 +2x - 5)$ ?

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Answer 1 · 2015-06-25T08:16:07

$= color(blue)(x^3 + 6x^2 + 3x -20$

$color(blue)((x+4))(x^2 +2 x - 5)$

Here, we first multiply $color(blue)(x)$ contained in the first bracket with all three terms of second bracket:

$= color(blue)(x).(x^2) + color(blue)(x) .(2 x) + color(blue)(x) . (-5)$

$= x^3 + 2x^2 -5x$ ........................ $(1)$

Now, we multiply $color(blue)(4)$ contained in the first bracket with all three terms of second bracket:

$= color(blue)(4).(x^2) + color(blue)(4) . 2x + color(blue)(4) . (-5)$

$= 4x^2 + 8x -20$ ......................... $(2)$

combining $(1)$ and $(2)$

$= color(blue)(x^3 + 6x^2 + 3x -20$

How do you multiply (x+4)(x^2 +2x - 5)(x+4)(x^2 +2x - 5)?