Помогите срочно 451....452 УМОЛЯЮЮЮ!!!!

451
$\frac{a^2-9}{2a^2}* \frac{a}{2a+6}= \frac{(a-3)*(a+3)*a}{2a^2*2*(a+3)}= \frac{a-3}{4a} \\ \\ a= \frac{1}{27} \\ \\ \frac{ \frac{1}{27}-3}{4* \frac{1}{27}}=-2 \frac{26}{27}: \frac{4}{27}=- \frac{80*27}{27*4}=-20$

452
$(\frac{4y}{5x}- \frac{5x}{4y}):(4y+5x)= \frac{16y^2-25x^2}{20xy}:(4y+5x)= \frac{(4y-5x)*(4y+5x)}{20xy*(4y+5x)}= \frac{4y-5x}{20xy} \\ \\ x= \frac{1}{5},y= \frac{1}{8} \\ \\ \frac{4* \frac{1}{8}-5* \frac{1}{5}}{20* \frac{1}{5}* \frac{1}{8}}= \frac{ \frac{1}{2}-1}{ \frac{1}{2} }=- \frac{ \frac{1}{2} }{ \frac{1}{2} }= -1$