exam Maths Puzzle Numerical Ability

please help me with this I really do not understand what to do.
if f(x)=5x-1 find the following,
f(-2)

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exam Other Question

If the discriminat is negative, would this be a true statement?

The discriminant is negative, so the quadratic has no real-valued zeroes and therefore no solution.
If logk4=2/3 then k=?

Thank you