Is power negative or positive for concave lens ?

Graph of position of image vs position of point object from a convex lens is shown. Then, focal length of the lens is

Give scientific reasons for the following statements: To rectify the defect of near-sightedness or myopia, concave lens of suitable focal length is used as corrective lens.

Depending on in which quadrant an angle theta lies, functions costheta and sintheta may be positive or negative. In the second column of the given lable are specified whether these functions are positive or negative and in the first column are specified quadrants. {:("Column-I","Column-II"),((A)" First",(P)sintheta" is positive"),((B)" Second",(Q)sintheta" is negative"),((C)" Third",(R)costheta" is negative"),((D)" Fourth",(S)tantheta" and "sintheta"both are negative"),(,(T)sectheta" is negative and "sintheta" is positive"):}

What will be change in speed of moving object if both speed and acceleration are positive or negative?

A current of two amperes is flowing through a cell of e.m.f. 5 volts and internal resistance 0.5 ohm from negative to positive electrode. If the potential of negative electrode is 10 V , the potential of positive electrode will be

Convex lens having focal length f, and concave lens having focal length f2 are placed in contact. Out of conditions given below, which condition supports this combination to behave like concave lens ?

Far-sightedness can be rectified by using a concave lens of suitable power.

It work done positive or negative for stretched spring ?