document.write( "Question 235864: x^2-4x-21=0
\n" ); document.write( "we must find Δ in oder to know in which conditions this equation must be solved.
\n" ); document.write( "Δ=((-b)^2-4*a*c)
\n" ); document.write( "(*)if Δ>0 this equation has 2 solutions x=(-bą√Δ)/2a.
\n" ); document.write( "(**)if Δ=0 this equation has only one solution x=-b/2a.
\n" ); document.write( "(***)if Δ<0 this equation must be solved by a transformation of Δ to a complex number.
\n" ); document.write( "if we apply Δ's formula:
\n" ); document.write( "Δ=(-(-4))^2-4*(-21)=100 then Δ>0 so we must refered to condition(*)in oder to solve this equation.
\n" ); document.write( "√Δ=10
\n" ); document.write( "this equation has 2 results x1,x2.
\n" ); document.write( "x1=(-(-4)-10)/2; x2=(-(-4)+10)/2
\n" ); document.write( " x1=-3;x2=7
\n" ); document.write( "
\n" ); document.write( " S={-3;7}
\n" ); document.write( " \n" ); document.write( "

Algebra.Com's Answer #173616 by checkley77(12844) $\"\"$ $\"About$

You can put this solution on YOUR website!
x^2-4x-21
\n" ); document.write( "(x-7)(x+3) ans. \n" ); document.write( "

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