Question:

The line \(y=mx+2\) is a tangent to the parabola \(y^2=8x\) if

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For \(y^2=4ax\), tangent with slope \(m\) is \(y=mx+\frac{a}{m}\).
  • \(m=1\)
  • \(m=2\)
  • \(m=3\)
  • \(m=4\)
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The Correct Option is A

Solution and Explanation

Concept: For the parabola: \[ y^2=4ax \] the tangent with slope \(m\) is: \[ y=mx+\frac{a}{m} \]

Step 1:
Given parabola: \[ y^2=8x \] Compare with: \[ y^2=4ax \] \[ 4a=8 \] \[ a=2 \]

Step 2:
Standard tangent equation is: \[ y=mx+\frac{a}{m} \] Substitute \(a=2\): \[ y=mx+\frac{2}{m} \]

Step 3:
Given line is: \[ y=mx+2 \] So comparing constant terms: \[ \frac{2}{m}=2 \] \[ m=1 \] Therefore, \[ \boxed{m=1} \]
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