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The equation of the straight line representing the tangent to the curve \(y = x^{2}\) at the point (1,1) is

  • A.\(y = 2x - 2\)
  • B.\(x = 2y - 1\)
  • C.\(y - 1 = 2(x - 1)\)
  • D.\(x - 1 = 2(y - 1)\)

Answer: C

The tangent is y - 1 = 2(x - 1).

The slope of \(y = x^{2}\) is \(dy/dx = 2x\), which is 2 at x = 1. The point-slope form through (1,1) is therefore y - 1 = 2(x - 1), that is, y = 2x - 1.

y = 2x - 2 has the right slope but passes through (1, 0), not (1, 1). x = 2y - 1 and x - 1 = 2(y - 1) have slope 1/2, which comes from swapping x and y, the tangent to the inverse curve.

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