$45:\left(-5\right)-6\:.\:\left(-4\right)-\left(-5\right)\:.\:\left(-3\right)$

$\lim_{x\to\infty}\left(\frac{2x-5}{x+3-5^{\frac{1}{x}}}\right)$

$\sqrt{\frac{9-x^2}{9+x^2}}$

$\left(-10\right)\left(-5\right)\left(-2\right)$

$\left(\frac{3}{5}x+\frac{5}{3}\right)^2$

$9\left(-8\right)^2-6\left(-5\right)^2$

$5x-7y=21$