How do you solve using the completing the square method #3x^2 + 11x – 20 = 0#?
1 Answer
May 2, 2016
Explanation:
Premultiply by
#a^2-b^2=(a-b)(a+b)#
with
#0 = 12(3x^2+11x-20)#
#=36x^2+132x-240#
#=(6x)^2+2(6x)(11)-240#
#=(6x+11)^2-121-240#
#=(6x+11)^2-361#
#=(6x+11)^2-19^2#
#=((6x+11)-19)((6x+11)+19)#
#=(6x-8)(6x+30)#
#=(2(3x-4))(6(x+5))#
#=12(3x-4)(x+5)#
Hence