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The line l contains the points A(4, 5) and B(2, 0) - Leaving Cert Mathematics - Question 4 - 2016

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The line l contains the points A(4, 5) and B(2, 0). Find the equation of l. Give your answer in the form ax + by + c = 0 where a, b, and c ∈ Z. (b) Draw the line k:... show full transcript

Worked Solution & Example Answer:The line l contains the points A(4, 5) and B(2, 0) - Leaving Cert Mathematics - Question 4 - 2016

Step 1

Use a graphic, numeric or algebraic method to find the co-ordinates of l ∩ k

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Answer

To find the intersection of lines l and k, we can substitute the equation from line k into line l:

  1. Start with line k: x+2y=8x + 2y = 8 Rearranging gives: 2y=8xy=412x2y = 8 - x \quad \Rightarrow y = 4 - \frac{1}{2}x

  2. Substitute into line l: 5x2y+10=05x - 2y + 10 = 0 Replace y with our expression from line k: 5x2(412x)+10=05x - 2(4 - \frac{1}{2}x) + 10 = 0 5x8+x+10=05x - 8 + x + 10 = 0 6x+2=0x=136x + 2 = 0 \Rightarrow x = -\frac{1}{3}

Substituting x back into the equation for y: y=412(13)=4+16=24+16=256y = 4 - \frac{1}{2}(-\frac{1}{3}) = 4 + \frac{1}{6} = \frac{24 + 1}{6} = \frac{25}{6}

Thus, the intersection point l ∩ k is:

(3,2)(3, 2)

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