Line Intersections 720F63
1. **State the problem:** Find the intersection point of the first pair of lines: $$y = -4x + 1$$ and $$y = 4x + 2$$.
2. **Set the equations equal to find the intersection:** Since both equal $$y$$, set $$-4x + 1 = 4x + 2$$.
3. **Solve for $$x$$:**
$$-4x + 1 = 4x + 2$$
$$1 - 2 = 4x + 4x$$
$$-1 = 8x$$
$$x = -\frac{1}{8}$$
4. **Find $$y$$ by substituting $$x$$ back into one of the equations:**
Using $$y = -4x + 1$$:
$$y = -4\left(-\frac{1}{8}\right) + 1 = \frac{1}{2} + 1 = \frac{3}{2}$$
5. **Intersection point:** $$\left(-\frac{1}{8}, \frac{3}{2}\right)$$
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6. **State the problem:** Find the intersection point of the second pair: $$y = \frac{2}{3}x - 5$$ and $$y = \frac{2}{3}x + 6$$.
7. **Set equal:** $$\frac{2}{3}x - 5 = \frac{2}{3}x + 6$$
8. **Simplify:** Subtract $$\frac{2}{3}x$$ from both sides:
$$-5 = 6$$
This is a contradiction, so **no intersection**.
These lines are parallel because they have the same slope but different intercepts.
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9. **State the problem:** Find the intersection point of the third pair: $$y = \frac{2}{5}x - 3$$ and $$y = \frac{5}{2}x - 3$$.
10. **Set equal:**
$$\frac{2}{5}x - 3 = \frac{5}{2}x - 3$$
11. **Simplify:** Add 3 to both sides:
$$\frac{2}{5}x = \frac{5}{2}x$$
12. **Subtract $$\frac{2}{5}x$$ from both sides:**
$$0 = \frac{5}{2}x - \frac{2}{5}x = \left(\frac{25}{10} - \frac{4}{10}\right)x = \frac{21}{10}x$$
13. **Solve:**
$$\frac{21}{10}x = 0 \implies x = 0$$
14. **Find $$y$$:** Substitute $$x=0$$ into either equation:
$$y = \frac{2}{5} \times 0 - 3 = -3$$
15. **Intersection point:** $$\left(0, -3\right)$$
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16. **State the problem:** Find the intersection point of the fourth pair: $$y = -6x + 4$$ and $$y = \frac{1}{6}x - 7$$.
17. **Set equal:**
$$-6x + 4 = \frac{1}{6}x - 7$$
18. **Multiply both sides by 6 to clear denominator:**
$$6(-6x + 4) = 6\left(\frac{1}{6}x - 7\right)$$
$$-36x + 24 = x - 42$$
19. **Bring all terms to one side:**
$$-36x - x = -42 - 24$$
$$-37x = -66$$
20. **Solve for $$x$$:**
$$x = \frac{66}{37}$$
21. **Find $$y$$:** Substitute into $$y = -6x + 4$$:
$$y = -6 \times \frac{66}{37} + 4 = -\frac{396}{37} + \frac{148}{37} = -\frac{248}{37}$$
22. **Intersection point:** $$\left(\frac{66}{37}, -\frac{248}{37}\right)$$