| $(x,y)$ |
|---|
| $(0,81)$ |
| $(1,80)$ |
| $(2,77)$ |
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]
ความรู้ที่ใช้ : ฟังก์ชัน
