what is the image value of -3 under f+g if f(x) =3x^3 -5x^2 +4x -6 and g (x) =-8x^2 - 7x +12?
a. -183
b.51
c.-21
d.213

Question

what is the image value of -3 under f+g if f(x) =3x^3 -5x^2 +4x -6 and g (x) =-8x^2 - 7x +12?
a. -183  
b.51
c.-21
d.213

anonymous · Answer

this is kinda longg

ash2326 · Answer

we have 
$$f(x)=3x^3 -5x^2 +4x -6$$
and $$g(x)=-8x^2-7x+12$$
$$f+g=3x^3-5x^2+4x-6-8x^2-7x+12$$
combining like terms, we get
$$f+g=3x^3-13x^2-3x+6$$
we want to find image value of -3 under f+g which is same as value of f+g for x=-3
substitute x=-3 in f+g, we get
$$f(-3)+g(-3)=3*(-27)-13(9)+9+6$$
or 
$$f(-3)+g(-3)=-81-117+9+6$$
or
$$f(-3)+g(-3)=-183$$
option A

anonymous · Answer

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