Let "f(x)=ax^2+bx+c, a\\not=0." Then the discriminant if "f(x)" is
The equation "f(x)=6x-18" has exactly one root
"ax^2+(b-6)x+(c+18)=0"
"(b-6)^2-4a(c+18)=0"
The equation "f(x)=9-3x" has exactly one root
"ax^2+(b+3)x+(c-9)=0"
"(b+3)^2-4a(c-9)=0"
We have the system
"b^2-4ac=12b+72a-36""b^2-4ac=-6b-36a-9"
"12b+72a-36=-6b-36a-9"
"b=-6a+1.5""b^2-4ac=36a-9-36a-9"
"D=-18"
The value of the discriminant of "f(x)" is "-18."
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