If a number is subtracted from five times its square, the result is eighteen. Find all such numbers.:If there is more than one answer, separate them with the "and" button.:If there is no such number, select the "None" button.

Solution

I f a n u mb er i s s u b t r a c t e d f ro m f i v e t im es i t s s q u a re, t h e res u lt i s e i g h t ee n . F in d a ll s u c h n u mb ers . : I f t h ere i s m ore t han o n e an s w er, se p a r a t e t h e m w i t h t h e " an d " b u tt o n . : I f t h ere i s n o s u c h n u mb er, se l ec t t h e " N o n e " b u tt o n .

The number : 2 or - 1 \frac{4}{5}

Solution steps

Represent the number with

x

A.T.Q.:

5 x^{2} - x = 18

Solve for

x, 5 x^{2} - x = 18 : x = 2, x = - \frac{9}{5}

Convert improper fractions to mixed numbers:

\frac{9}{5} = 1 \frac{4}{5}

The number : 2 or - 1 \frac{4}{5}