20.997
1) Let's start by dividing from 0 to 4 into n equal subintervals:
[tex]n=4,x=\frac{(4-0)}{4}=1[/tex]
So the width of each rectangle is going to be 1
2) The next step is to calculate the area below the curve using the right endpoints using the following intervals:
[tex]\lbrack0,1\rbrack,\lbrack1,2\rbrack,\lbrack2,3\rbrack,\lbrack3,4\rbrack[/tex]
And plug each endpoint into that we have:
[tex]\begin{gathered} R_4=f(x_1)\cdot x+f(x_2)x+f(x_3)x+f(x_4)x \\ R_4=f(1)\cdot1+f(2)\cdot1+f(3)\cdot1+f(4)\cdot1 \\ R_4=(\sqrt[]{9(1)+6})\cdot1+(\sqrt[]{9(2)+6})\cdot1+(\sqrt[]{9(3)+6})\cdot1+(\sqrt[]{9(4)+6})\cdot1 \\ R_4=\sqrt[]{15}+2\sqrt[]{6}+\sqrt[]{33}+\sqrt[]{42}\approx20.997 \end{gathered}[/tex]
Note that since each rectangle has a width of 1 unit, we could plug it into that.
3) Hence, the answer is approximately 20.997