1987 年

$\left(\dfrac{x+1}{x}\right)^2-\left(\dfrac{x-1}{x}\right)^2=$

If $\dfrac{1}{x}-\dfrac{1}{y}=\dfrac{1}{z}$, and $x=\dfrac{1}{2}$, $z=\dfrac{1}{3}$, then $y=$

If $a=\dfrac{b+3cd}{b-3cd}$, then $c=$

The radii of two solid spheres made of the same material are in the ratio $2:3$. If the smaller sphere weighs 16 kg, then the larger one weighs

Given that $x\ne0$ and $-x$, $x$, $3x^2$ are in G.P., find $x$.

If $x+\dfrac{1}{x}=1+\sqrt{2}$, then $x^2+\dfrac{1}{x^2}=$

When the expression $x^2+px+q$ is divided by $x+1$, the remainder is 4. Find the value of $2p-2q+1$.

In the figure, the graph of $y=x^2+bx+c$ cuts the $x$-axis at $A$ and $B$. $OA+OB=$

If $\mathrm{f}(x)=x^2+1$, then $\mathrm{f}(x-1)=$

If $\log_{10}x$, $\log_{10}y$, $\log_{10}z$ are in A.P., then