[tex]a.\ 7\times6=42\\\\b.\ \sqrt{729}=27\ \text{because}\ 27^2=729[/tex]
[tex] c.\ |x+3|=2x+5\\\\|x+3|=\left\{\begin{array}{ccc}x+3&for&x\geq-3\\-x-3&for&x < -3\end{array}\right\\\\(1)\ x < -3\to x\in(-\infty;\ -3)\\\\-x-3=2x+5\ \ \ |+3\\\\-x=2x+8\ \ \ |-2x\\\\-3x=8\ \ \ \ |:(-3)\\\\x=-\dfrac{8}{3}\\\\x=-2\dfrac{2}{3}\notin(-\infty;\ -3)\\\\(2)\ x\geq-3\to x\in\left<-3;\ \infty\right)\\\\x+3=2x+5\ \ \ \ |-3\\\\x=2x+2\ \ \ \ |-2x\\\\-x=2\ \ \ |\cdot(-1)\\\\x=-2\in\left<-3;\ \infty\right)\\\\Answer:\ x=-2 [/tex]
