Resposta :
[tex]x^2-8x+k-1=0\\\\x^2-8x+k-1-\left(x^2-8x\right)=0-\left(x^2-8x\right)\\\\k-1=-\left(x^2-8x\right)\\\\k-1+1=-\left(x^2-8x\right)+1\\\\k=-x^2+8x+1[/tex]
[tex]x^2-8x+k-1=0\\\\x^2-8x+k-1-\left(x^2-8x\right)=0-\left(x^2-8x\right)\\\\k-1=-\left(x^2-8x\right)\\\\k-1+1=-\left(x^2-8x\right)+1\\\\k=-x^2+8x+1[/tex]