Question 150958
{{{f(x)=0.004x^3-0.15x^2+4.9x + 7}}} Start with the given equation.



{{{f(30)=0.004(30)^3-0.15(30)^2+4.9(30) + 7}}} Plug in {{{x=30}}}.



{{{f(30)=0.004(27000)-0.15(30)^2+4.9(30)+7}}} Cube {{{30}}} to get {{{27000}}}.



{{{f(30)=0.004(27000)-0.15(900)+4.9(30)+7}}} Square {{{30}}} to get {{{900}}}.



{{{f(30)=108-0.15(900)+4.9(30)+7}}} Multiply 0.004 and 27,000 to get 108



{{{f(30)=108-135+4.9(30)+7}}} Multiply -0.15 and 900 to get -135



{{{f(30)=108-135+147+7}}} Multiply 4.9 and 30 to get 147



{{{f(30)=127}}} Combine like terms



So the height is 127 units (you forgot to include the units in the problem) when {{{x=30}}}