Question 825039
Here's another way to write this: {{{8*x+5 = x^2+20}}} (x is the unknown number)
First subtract the right side from the equation, therefore moving it to the left side. {{{8*x+5-x^2-20 = 0}}}
Combine like terms. {{{-x^2+8*x-15 = 0}}}
This is a quadratic equation, which can be solved using the quadratic formula: {{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}
Enter the values into the formula and simplify until you have your answer.
{{{x = (-(8) +- sqrt( (8)^2-4*(-1)*(-15) ))/(2*(-1)) }}}
{{{x = (-8 +- sqrt( 64-60 ))/-2 }}}
{{{x = (-8 +- sqrt( 4 ))/-2 }}}
{{{x = (-8 +- 2)/-2 }}}
This problem has two possible solutions.
Solution 1:
{{{x = -6/-2 }}}
{{{x = 3}}}
Solution 2:
{{{x = -10/-2 }}}
{{{x = 5}}}
The number is 3 or 5.