Mr. Alex's answer to Ng Keat's Secondary 3 A Maths question.
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A tangent touches a curve only at one point. Hence, if you use simultaneous equation to solve for the intersection point, you will get real and equal root. For real and equal root, b^2-4ac=0. Hence, if you can show that D=0, you have proven that the line is a tangent for all values of k.
Date Posted:
6 years ago