# IIT JEE circle hyperbola common tangent part 2 | Conic sections | Algebra II | Khan Academy | Summary and Q&A

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December 21, 2010
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IIT JEE circle hyperbola common tangent part 2 | Conic sections | Algebra II | Khan Academy

## TL;DR

The video explains how to find the constraints on the slope and y-intercept of a line that is tangent to a circle.

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### Q: How can the quadratic formula help determine the intersection point(s) between a line and a circle?

The quadratic formula can be used to find the x values of the intersection point(s) by solving the quadratic equation derived from substituting the line equation into the circle equation.

### Q: What conditions must be met for a line to be tangent to a circle?

A line is tangent to a circle if and only if it intersects the circle at exactly one point. This can be determined by setting b squared minus 4ac equal to 0 in the quadratic equation.

### Q: How can the slope and y-intercept of a tangent line be expressed in terms of each other?

By using the quadratic formula to solve for y-intercept in terms of slope, the relationship between the two can be determined, revealing the constraints on their values.

### Q: How does the quadratic formula help find the constraints on the slope and y-intercept?

By solving the resulting quadratic equation and analyzing its discriminant (b squared minus 4ac), the constraints on the slope and y-intercept can be determined.

## Summary & Key Takeaways

• The video discusses finding the constraints on the slope and y-intercept of a line that is tangent to a circle.

• By substituting the equation of the line into the equation of the circle, the quadratic equation can be solved to determine the intersection point(s).

• The quadratic equation will only have one solution if the line is tangent to the circle.