Given the equation sinx+4ylog(2y)=5. First, differentiate both sides with respect to x: dxd(sinx)+dxd(4ylog(2y))=dxd(5) We know that dxd(sinx)=cosx and dxd(5)=0. So, cosx+dxd(4ylog(2y))=0. Now we need to find the derivative of 4ylog(2y) with respect to x. We'll use the quotient rule: dxd(vu)=v2vdxdu−udxdv Let u=log(2y) and v=4y. Then dxdu=2y1⋅2⋅dxdy=y1dxdy and dxdv=4dxdy. So,
dxd(4ylog(2y))=(4y)24y⋅y1dxdy−log(2y)⋅4dxdy=16y24dxdy−4log(2y)dxdy=16y24(1−log(2y))dxdy=4y2(1−log(2y))dxdy Now, plug this back into the original differentiated equation:
cosx+4y2(1−log(2y))dxdy=0 Now, solve for dxdy: 4y2(1−log(2y))dxdy=−cosx dxdy=1−log(2y)−4y2cosx=log(2y)−14y2cosx Multiply both the numerator and denominator by -1:
dxdy=−1−log(2y)4y2cosx. The given solution is:
dxdy=−4−log(2y)3y2cosx The correct derivative of log(2y) with respect to x is 2y1∗2∗dxdy=y1dxdy. The correct derivative of 4y with respect to x is 4dxdy. Using quotient rule on 4ylog(2y) will give: (4y)24y∗y1dxdy−log(2y)∗4dxdy=16y24dxdy−4log(2y)dxdy=4y2(1−log(2y))dxdy. Therefore dxdy=−1−log(2y)4y2cos(x). The question must be a copy error. The equation for dxdy is most probably: dxdy=−4−log(2y)4y2cosx. This gives:
cosx+dxdy4y21−log(2y)=0 dxdy4y21−log(2y)=−cosx dxdy=−1−log(2y)4y2cosx If we wish to obtain −4−log(2y)3y2cosx, there is no algebraic way from the given equation.