Question : If $m^2-n^2=21$ and $m - n = 3$, find the value of $m + n$.

Option 1: 7

Option 2: 4

Option 3: 24

Option 4: 18

Question : If $m+n=-2$, then the value of $m^{3}+n^{3}-6mn$ is:

Option 1: 8

Option 2: 4

Option 3: –8

Option 4: –4

Question : If $\cos 20°= m$ and $\cos 70°=n$, then the value of $m^2+n^2$:

Option 1: $1$

Option 2: $\frac{3}{2}$

Option 3: $\frac{1}{\sqrt2}$

Option 4: $\frac{1}{2}$

Question : In a star network, how many lines are required for connecting N nodes to the host node?

Option 1: N + 1

Option 2: N/2

Option 3: (N/2) – 1

Option 4: N – 1

Question : If $l+m+n=0$, then what will be the value of $(\frac{l^2}{mn}+\frac{m^2}{nl}+\frac{n^2}{lm})^2$?

Option 1: 9

Option 2: 16

Option 3: 4

Option 4: 1