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The diagram shows the graph of $x^2 + y^2 = 30.25$ - Edexcel - GCSE Maths - Question 20 - 2021 - Paper 1

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The diagram shows the graph of $x^2 + y^2 = 30.25$. Use the graph to find estimates for the solutions of the simultaneous equations $x^2 + y^2 = 30.25$ y - 2x =... show full transcript

Worked Solution & Example Answer:The diagram shows the graph of $x^2 + y^2 = 30.25$ - Edexcel - GCSE Maths - Question 20 - 2021 - Paper 1

Step 1

y - 2x = 1

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Answer

To find the points of intersection between the circle and the line defined by the equation y2x=1y - 2x = 1, we can rearrange the equation to express y: y=2x+1y = 2x + 1.

Now we substitute this expression into the first equation: x2+(2x+1)2=30.25x^2 + (2x + 1)^2 = 30.25 Expanding this: x2+(4x2+4x+1)=30.25x^2 + (4x^2 + 4x + 1) = 30.25 Combining like terms: 5x2+4x+130.25=05x^2 + 4x + 1 - 30.25 = 0 Thus: 5x2+4x29.25=05x^2 + 4x - 29.25 = 0 Using the graph, at the intersections, we can estimate the values for x. From the graph, we can approximate two pairs of (x, y) values for the intersection points:

  1. xextapproximately2.2x ext{ approximately } 2.2, then substituting to find yy: y=2(2.2)+1extapproximately5.4y = 2(2.2) + 1 ext{ approximately } 5.4. So, one estimated coordinate is (2.2,5.4)(2.2, 5.4).
  2. xextapproximately4.6x ext{ approximately } -4.6, then substituting to find yy: y=2(4.6)+1extapproximately8.2y = 2(-4.6) + 1 ext{ approximately } -8.2. So, another estimated coordinate is (4.6,8.2)(-4.6, -8.2).

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