How do you graph (3x + 3) / (2x + 4)3x+32x+4?

1 Answer
Jul 6, 2015

Separate into a polynomial (constant) term and rational expression that tends to zero as x -> +-oox±. Deduce asymptotic behaviour.

Explanation:

f(x) = (3x+3)/(2x+4) = (3(x+1))/(2(x+2)) = 3/2*(x+1)/(x+2)f(x)=3x+32x+4=3(x+1)2(x+2)=32x+1x+2

=3/2*(x+2-1)/(x+2)=32x+21x+2

=3/2((x+2)/(x+2)-1/(x+2))=32(x+2x+21x+2)

=3/2(1-1/(x+2))=32(11x+2)

=3/2-3/(2(x+2))=3232(x+2)

with exclusion x != -2x2

So as x->-oox the term 3/(2(x+2)) ->0_-32(x+2)0 so f(x)->(3/2)_+f(x)(32)+

As x->(-2)_-x(2) the term 3/(2(x+2))->-oo32(x+2) so f(x)->oof(x)

As x->(-2)_+x(2)+ the term 3/(2(x+2))->oo32(x+2) so f(x)->-oof(x)

As x->oox the term 3/(2(x+2)) -> 0_+32(x+2)0+ so f(x)->(3/2)_-f(x)(32)

The intersection with the xx axis occurs at (-1, 0)(1,0) since the numerator of the original expression is 00 for x = -1x=1

The intersection with the yy axis can be found by substituting x=0x=0 into the original equation to derive (0, 3/4)(0,34)

graph{ (3x+3)/(2x+4) [-12.29, 7.71, -3.44, 6.56]}