# SOLUTION: f(x)= -2x^3-2x find x if f(x) =-49

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 Algebra: Functions, Domain, NOT graphing Solvers Lessons Answers archive Quiz In Depth

 Question 204837: f(x)= -2x^3-2x find x if f(x) =-49Found 2 solutions by checkley77, RAY100:Answer by checkley77(12569)   (Show Source): You can put this solution on YOUR website!f(x)=-2x^3-2x find x if f(x)=-49 f(-49)=-2(-49^3)-2*-49 f(-49)=-2*-117,649+98 f(-49)=235,298+98 f(-49)=235,396 ans. Answer by RAY100(1637)   (Show Source): You can put this solution on YOUR website!With deference to my esteemed college..perhaps we should try . f(x) = -2x^3 -2x =-49,,,when x=? . or -2x^3 -2x +49 =0,,,,solve for x. . In general this is a negative cubic function. . On the x-y coordinate system, this drops from top left to bottom right, with 2 (3-1) turns, and normally 3 answers. . Normally we would factor the function, to find the zero's. . However after much work, we plotted the function and found that two of the zeros are imaginary. The function does drop and does turn twice, but it only crosses the x axis once, hence 2 imaginary Zeros (3-1=2) . The x intercept is at about (2.789, 0) . checking: substitute in original function . -2(2.789)^3 -2(2.789) =49 ,,,,,,ok . Have a great weekend