The volume of square pyramid is 141 2/3 cubic inches. The height of the pyramid is two more than three times the lenght of its base . What is the lenght of the base?

Respuesta :

[tex]\bf \textit{volume of a pyramid}\\\\ V=\cfrac{1}{3}Bh\qquad \begin{cases} B=base=length\times width\\\\ h=height\\ ----------\\ \textit{for a square pyramid}\\ \textit{the base is a square}\\ \textit{thus length=width=x}\\ B=x\cdot x=x^2\\ ----------\\ V=141\frac{2}{3}\\\\ h=3x+2 \end{cases}[/tex]

[tex]\bf V=\cfrac{1}{3}Bh\implies 141\frac{2}{3}=x^2(3x+2) \\\\\\ \cfrac{425}{3}=3x^3+2x^2\implies 425=9x^3+6x^2\implies 0=9x^3+6x^2-425[/tex]

solve for "x"

hmm I tried factoring it, tried a few combos, no dice, haven't graphed it

but, it doesn't seem it factor that neatly, so the solutions are likely decimals with long floats