Question 421079


{{{3}}} times a number is {{{28}}} less than the square of that number

let a number be {{{x}}}

{{{3x+28=x^2}}}

{{{x^2-3x-28=0}}}


{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}}

{{{x = (-(-3) +- sqrt( (-3)^2-4*1*(-28) ))/(2*1) }}}

{{{x = (3 +- sqrt( 9 + 112 ))/2 }}}

{{{x = (3 +- sqrt(  121 ))/2 }}}

{{{x = (3 +- (  11))/2 }}}

positive solution

{{{x = (3 +  11)/2 }}}

{{{x =  14/2 }}}

{{{x =  7 }}}

check:

{{{3x+28=x^2}}}

{{{3*7+28=7^2}}}

{{{21+28=49}}}

{{{49=49}}}