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

1 Answer
Don't Memorise
Jun 25, 2015

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

Explanation:

#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#

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