Answer:
The equation that describe the situation is
![b^(3)-9b^(2)-18,900=0](https://img.qammunity.org/2020/formulas/mathematics/high-school/britb8zqjzbaftzywej8pcrplxef2bncpo.png)
Explanation:
we know that
The volume of a square pyramid is equal to
![V=(1)/(3)b^(2) h](https://img.qammunity.org/2020/formulas/mathematics/high-school/maj9iekkb42c98p7zazoqrevlmwbmwibpv.png)
where
b is the length side of the square
h is the height of the pyramid
we have
![V=6,300\ in^(3)](https://img.qammunity.org/2020/formulas/mathematics/high-school/iz7xc9moh6ccmhpue3r2dkkvpkpq38nuyp.png)
![h=(b-9)\ in](https://img.qammunity.org/2020/formulas/mathematics/high-school/islkdjs7j0ncx28nlaqsldsp8skbks6u3j.png)
substitute the values and solve for b
![6,300=(1)/(3)b^(2) (b-9)\\ \\18,900=[b^(3)-9b^(2)]\\ \\b^(3)-9b^(2)-18,900=0](https://img.qammunity.org/2020/formulas/mathematics/high-school/g2g345ihp77can1b1ap5nyrk61wl21drg4.png)
Using a graphing calculator
![b=30\ in](https://img.qammunity.org/2020/formulas/mathematics/high-school/jepcj3lvam7mv48pozxbp0s7bj9319g73m.png)
![h=(30-9)=21\ in](https://img.qammunity.org/2020/formulas/mathematics/high-school/2xco1ra128yknp3mbgrje5q7z3jotn8hrm.png)