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1966 AMC 12 Question 22

AMC12 · 1966 AMC 12

Question 22

Consider the statements:

$$
\text{(I) }\sqrt{a^2+b^2}=0
$$ $$
\text{(II) }\sqrt{a^2+b^2}=ab
$$ $$
\text{(III) }\sqrt{a^2+b^2}=a+b
$$ $$
\text{(IV) }\sqrt{a^2+b^2}=a-b
$$

where we allow $a$ and $b$ to be real or complex numbers. Those statements for which there exist solutions other than $a=0$ and $b=0,$ are:
  1. $(\mathrm{I}),$ $(\mathrm{II}),$
    $(\mathrm{III}),$ $(\mathrm{IV})$
  2. $(\mathrm{II}),$ $(\mathrm{III}),$ $(\mathrm{IV})$
    only
  3. $(\mathrm{I}),$ $(\mathrm{III}),$ $(\mathrm{IV})$
    only
  4. $(\mathrm{III}),$ $(\mathrm{IV})$ only
  5. $(\mathrm{I})$ only