Start by expanding the parentheses.
4x^2 - 12x + 9 + 16y^2 - 40y + 25 = 104x2−12x+9+16y2−40y+25=10
d/dx(4x^2 - 12x + 9 + 16y^2 - 40y + 25) = d/dx(10)ddx(4x2−12x+9+16y2−40y+25)=ddx(10)
d/dx(4x^2) + d/dx(-12x) + d/dx(9) + d/dx(16y^2) + d/dx(-40y) + d/dx(25) = d/dx(10)ddx(4x2)+ddx(−12x)+ddx(9)+ddx(16y2)+ddx(−40y)+ddx(25)=ddx(10)
8x - 12 + 0 + 32y(dy/dx) - 40(dy/dx) + 0 = 08x−12+0+32y(dydx)−40(dydx)+0=0
32y(dy/dx) - 40(dy/dx) = 12 - 8x32y(dydx)−40(dydx)=12−8x
dy/dx(32y - 40) = 12 - 8xdydx(32y−40)=12−8x
dy/dx = (12 - 8x)/(32y - 40)dydx=12−8x32y−40
dy/dx = (4(3 - 2x))/(4(8y - 10))dydx=4(3−2x)4(8y−10)
dy/dx= (3- 2x)/(8y - 10)dydx=3−2x8y−10
Hopefully this helps!