$(x,y)$
$(0,81)$
$(1,80)$
$(2,77)$

Which of the following equations describes $y$ in terms of $x$ for all ordered pairs in the table above?

เฉลยละเอียด

[STEP]Try substitue $x$ and $y$ from the ordered pairs into each choice[/STEP]

Substitue $x=0$ and $y=81$ from $(0,81)$

 $81=81-0^2 A) ok$81=81-0$B) ok$81=81-2(0)$C) ok$81=81-4(0)$D) ok$81=81-81(0)$E) ok Substitue$x=1$and$y=80$from$(1,80)$$80=81-1^2$A) ok$80=81-1$B) ok$80=81-2(1)$C) wrong!$80=81-4(1)$D) wrong!$80=81-81(1)$E) wrong! Substitue$x=2$and$y=77$from$(2,77)$$77=81-2^2$A) ok$77=81-2$B) wrong! Therefore the correct answer is A) [ANS]$y=100-x^2\$[/ANS]

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