How do you find the limit of (2x-1)/(abs(2x^3 - x^2))2x1|2x3x2| as x is approaching 0.5 from the negative side?

1 Answer
Mar 6, 2015

Factor, then use definition and properties of the absolute value.

(2x-1)/abs(2x^3-x^2)=(2x-1)/(abs(x^2)abs(2x-1))=1/x^2(2x-1)/abs(2x-1)2x1|2x3x2|=2x1|x2||2x1|=1x22x1|2x1|

As xrarr1/2x12 (from either side), 1/x^2rarr41x24

For x<0.5x<0.5, we have 2x<12x<1 and 2x-1<02x1<0.

Hence, for x<0.5x<0.5, we get

abs(2x-1)=-(2x-1)|2x1|=(2x1) and

(2x-1)/abs(2x-1)=(2x-1)/-(2x-1)=-12x1|2x1|=2x1(2x1)=1.

Therefore, as xrarr1/2x12 from the negative side, (2x-1)/abs(2x^3-x^2)rarr(4)(-1)=-42x1|2x3x2|(4)(1)=4.