Photo AI

Figure 2 shows the line with equation $y = 10 - x$ and the curve with equation $y = 10x - x^2 - 8$ - Edexcel - A-Level Maths Pure - Question 7 - 2012 - Paper 3

Question icon

Question 7

Figure-2-shows-the-line-with-equation-$y-=-10---x$-and-the-curve-with-equation-$y-=-10x---x^2---8$-Edexcel-A-Level Maths Pure-Question 7-2012-Paper 3.png

Figure 2 shows the line with equation $y = 10 - x$ and the curve with equation $y = 10x - x^2 - 8$. The line and the curve intersect at the points A and B, and O is... show full transcript

Worked Solution & Example Answer:Figure 2 shows the line with equation $y = 10 - x$ and the curve with equation $y = 10x - x^2 - 8$ - Edexcel - A-Level Maths Pure - Question 7 - 2012 - Paper 3

Step 1

Calculate the coordinates of A and the coordinates of B.

96%

114 rated

Answer

To find the coordinates of A and B, we need to set the equations of the line and the curve equal to each other:

10x=10xx2810 - x = 10x - x^2 - 8

Rearranging gives us:

x211x+18=0x^2 - 11x + 18 = 0

Now we can solve this quadratic equation using the quadratic formula, where a=1a = 1, b=11b = -11, and c=18c = 18:

x=b±b24ac2a=11±(11)2411821=11±121722=11±492=11±72x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{11 \pm \sqrt{(-11)^2 - 4 \cdot 1 \cdot 18}}{2 \cdot 1} = \frac{11 \pm \sqrt{121 - 72}}{2} = \frac{11 \pm \sqrt{49}}{2} = \frac{11 \pm 7}{2}

Thus, the solutions for x are:

x1=182=9x_1 = \frac{18}{2} = 9 x2=42=2x_2 = \frac{4}{2} = 2

Now substituting these x-values back into the line equation to find the corresponding y-values:

For x=9x = 9:
y=109=1y = 10 - 9 = 1
Thus, one coordinate is A(9,1)A(9, 1).

For x=2x = 2:
y=102=8y = 10 - 2 = 8
Thus, the other coordinate is B(2,8)B(2, 8).

Step 2

Calculate the exact area of R.

99%

104 rated

Answer

The area R can be calculated by integrating the difference between the curve and the line from x=2x = 2 to x=9x = 9:

Area=29((10xx28)(10x))dxArea = \int_{2}^{9} ((10x - x^2 - 8) - (10 - x)) \, dx

Simplifying the integrand gives us:

Area=29(10xx2810+x)dx=29(11xx218)dxArea = \int_{2}^{9} (10x - x^2 - 8 - 10 + x) \, dx = \int_{2}^{9} (11x - x^2 - 18) \, dx

Calculating the integral:

=[11x22x3318x]29= \left[ \frac{11x^2}{2} - \frac{x^3}{3} - 18x \right]_{2}^{9}

Evaluating at the bounds:

At x=9x = 9:
=11(92)2(93)318(9)= \frac{11(9^2)}{2} - \frac{(9^3)}{3} - 18(9)
At x=2x = 2:
=11(22)2(23)318(2)= \frac{11(2^2)}{2} - \frac{(2^3)}{3} - 18(2)

Finally, calculate the differences to find the definite area R.

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;