z(x,y)=−6x^2−8y^2+3x+10y−10. Find the equation of the plane tangent to the graph of that equation. I found the partial derivative of x as -12x+3, and the y derivative as -16y+10. The point that they gave me was (9,-7). I plugged in 9 and -7 for x_o and y_o. I got −105x+122y+1799, and it's wrong. I also tried to set z_o as -10 (the last number in the original equation) and got −105x+122y+1789, which was also wrong.

Question

z(x,y)=−6x^2−8y^2+3x+10y−10. Find the equation of the plane tangent to the graph of that equation. I found the partial derivative of x as       -12x+3, and the y derivative as -16y+10. The point that they gave me was (9,-7). I plugged in 9 and -7 for x_o and y_o. I got −105x+122y+1799, and it's wrong. I also tried to set z_o as -10 (the last number in the original equation) and got −105x+122y+1789, which was also wrong.