6.1 Areas Between Curves/10

${\begin{aligned}&\color {red}\mathbf {y=1+{\sqrt {x}}} &\color {royalblue}\mathbf {y={\frac {3+x}{3}}} \\\\\end{aligned}}$

Failed to parse (unknown function "\begin{align}"): {\displaystyle \begin{align} 1+\sqrt{x} &= \frac{3+x}{3} \\ 1+\sqrt{x}-\frac{3+x}{3} &= 0 \\ \frac{3+3\sqrt{x}}{3}}-\frac{3+x}{3} &= 0 \\ 3+3\sqrt{x}-3+x &= 0 \\ 3\sqrt{x}+x &= 0 \\ 3\sqrt{x} &= -x \\ 9x &= x^2 \\ 9x-x^2 &= 0 \\ x(9-x) &= 0 \\ x &= 0,9 \\ \end{align} }