Question 460032
 {{{0.0013x^3 - 0.075x^2 + 1.5x + 11=23.1}}}


 {{{0.0013x^3 - 0.075x^2 + 1.5x =23.1-11}}}

{{{0.0013x^3 - 0.075x^2 + 1.5x =12.1}}}

{{{0.0013x^3 - 0.075x^2 + 1.5x -12.1=0}}}

let's see the graph first:


{{{ graph( 600, 600, -20, 50, -15, 30, 0.0013x^3 - 0.075x^2 + 1.5x -12.1) }}}

from the graph you see that only {{{x=29}}} is a real solution that might work

let's check it:

{{{0.0013x^3 - 0.075x^2 + 1.5x + 11=23.1}}}

{{{0.0013(29)^3 - 0.075(29)^2 + 1.5*29 + 11=23.1}}}

{{{0.0013(24389) - 0.075(841) + 1.5*29 + 11=23.1}}}

{{{31.7057 -63.075 + 43.5 + 11=23.1}}}

{{{86.2057 -63.075 =23.1}}}

{{{23.1307 =23.1}}}


if {{{x=0 }}}corresponds to {{{1960}}} then {{{x=29}}} corresponds to {{{1989}}}