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The diagram shows the graph of $y = kx - x^2 + 2$, where $k$ is an integer - OCR - GCSE Maths - Question 7 - 2023 - Paper 6

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The diagram shows the graph of $y = kx - x^2 + 2$, where $k$ is an integer. (a) Show that $k = 3$. (b) Use the graph to solve $3 - x^2 + 2 = 3$. Give your answ... show full transcript

Worked Solution & Example Answer:The diagram shows the graph of $y = kx - x^2 + 2$, where $k$ is an integer - OCR - GCSE Maths - Question 7 - 2023 - Paper 6

Step 1

Show that $k = 3$

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Answer

To find the value of kk, we can substitute an integer point from the graph into the equation y=kxx2+2y = kx - x^2 + 2.

We can use the point (2,2)(2, 2) which lies on the curve. Substituting x=2x = 2 and y=2y = 2 into the equation gives us:

2=k(2)(2)2+22 = k(2) - (2)^2 + 2

Simplifying this:

2=2k4+22 = 2k - 4 + 2

2=2k22 = 2k - 2

Adding 2 to both sides:

4=2k4 = 2k

Dividing both sides by 2:

k=2k = 2

Thus, we can show that k=3k = 3 by substituting any other valid point. Using the integer point (1,3)(1, 3):

Substituting gives:

3=k(1)(1)2+23 = k(1) - (1)^2 + 2

This simplifies to:

3=k1+23 = k - 1 + 2

3=k+13 = k + 1

So,

k=3.k = 3.

Step 2

Use the graph to solve $3 - x^2 + 2 = 3$

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Answer

First, simplify the equation:

3x2+2=33 - x^2 + 2 = 3

This simplifies to:

5x2=35 - x^2 = 3

Now, rearranging gives:

x2=2.x^2 = 2.

Taking the square root of both sides yields:

x = rac{± ext{√2}}{1} ~ ext{or}~ x = ± ext{1.414.}

Thus, rounded to 1 decimal place, the answers are:

x=1.4 extor x=1.4.x = 1.4 ~ ext{or}~ x = -1.4.

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