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As the tangent is a straight line, the equation of the tangent will be of the form y = m x + c. We can use perpendicular gradients to find the value of m, then use the coordinates of P to find the ...
4 = 9 4 + c 4 9 4 = c c = 25 4 So the equation of the tangent to the circle x 2 + y 2 = 25 at the point (3, -4) is y = 3 4 x 25 4 ...