The line is a tangent to the curve . What is the value of ?
Answer and explanation
Correct answer: B.
- Step 1: Set the expressions equal: , so .
- Step 2: A tangent gives a repeated root, so the discriminant is zero: .
- Step 3: Then , so and .
Answer
.
Why not the others: For , , or the discriminant of is , , or . None is zero, so none of these lines is a tangent.
Practise more Quadratics and the discriminant.
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