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Which of the following is NOT a quadratic equation after simplification?
A$(x-2)^2+1=2x-3$
B$x(x+1)+8=(x+2)(x-2)$
C$x(2x+3)=x^2+1$
D$(x+2)^3=x^3-4$
Answer & Solution
Correct answer: B. $x(x+1)+8=(x+2)(x-2)$
Simplify each equation first. In option B, $x(x+1)+8=x^2+x+8$ and $(x+2)(x-2)=x^2-4$, so the equation becomes $x+12=0$, which is linear, not quadratic. The other three simplify to equations of the form $ax^2+bx+c=0$.
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