1985 年

$\dfrac{\dfrac{b}{a}-\dfrac{a}{b}}{\dfrac{1}{a}-\dfrac{1}{b}}=$

If $\dfrac{ab}{ka+b}=\dfrac{1}{k}$, then $b=$

$(x+y)^{-1}(x^{-2}-y^{-2})=$

If $a-\sqrt{b^2+c^2}=d$, then $c=$

The L.C.M. of $2a^2-2b^2$ and $a^3-2a^2b+ab^2$ is

Let $a$ and $b$ be constants. If $3x^3-ax^2+5x-3b$ is divisible by $x+3$, then $3a+b=$

$\log_{10}(a^2-b^2)=$

If $\alpha$ and $\beta$ are roots of $x^2+2x-4=0$, then $2^{\alpha}\cdot 2^{\beta}=$

The second term and the fifth term of a geometric progression are $-12$ and $40\dfrac{1}{2}$ respectively. The first term is

If $a:b=1:2$ and $b:c=1:3$, then $a+b:b+c=$