Experts please solve these three questions:-
[i]What is The value of A in the equation [2x+7/4m]^2=4x^2+49/16m^2- 2Ax.
[ii]If m^2+4n^2=4mn,then the value of [m+n/m-n]is equal to which number.
[iii]If 7a-4b=17 and 14ab=42,then what is the value of teh expression 49a^2+16b^2?