How do you find all the zeros of #f(x) = 3x^2 − 4x − 15#?

2 Answers
Binayaka C.
Apr 7, 2018

Zeros of #f(x)# are #x=3 and x= -5/3#

Explanation:

#f(x)=3x^2-4x-15 =3x^2-9x+5x-15#

#=3x(x-3)+5(x-3)= (x-3)(3x+5)#

Zeros of #f(x)# are #x=3 and x= -5/3# [Ans]

Bounce light knowledge
Apr 7, 2018

#x=3,(-5)/3#

Explanation:

Using trial and error method #(x-3)# is a factor of #f(x)#
I.e#(x-3), x=3#
#f(3)=3(3^2)-4(3)-15#
#=3(9)-12-15#
#=27-12-15#
#=0#
Using long division of polynomial's
#(+)3x+5#
#root(x-3)(3x^2-4x-15)#
#((-)3x^2-9x)/(5x-15)#
#((-)5x-15)/(……)#
Since #x# is in the 2nd degree, the 2 factors of #f(x)#are #(x-3)# and #3x+5#
Equating factor to zero.
#x-3=0,3x+5=0#
#x=3,3x=-5#
#x=3,x=(-5)/3#(#color (blue) (zero's. Of.f(x))#)

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