Why does the expansion of -
[(e^x)/12 - 3(e^-x)]^2
contain a (-1/2)?
Note: when expanded --> [(e^2x)/144 - 9(e^-2x) -1/2]
Shouldn't it just be the first two terms?
Thanks in advance!
hi
the formula for the square of a difference is:
$\displaystyle (a-b)^2=a^2-2ab+b^2$
If $\displaystyle a=\frac{e^x}{12}$ and $\displaystyle b=\frac{3}{e^x}$
then:
$\displaystyle (a+b)^2=a^2+2ab+b^2=(\frac{e^x}{12})^2-2\cdot\frac{e^x}{12}\cdot\frac{3}{e^x}+(\frac{3}{e ^x}$
try it now.