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The curves $y = (x - 1)^2$ and $y = 5 - x^2$ intersect at two points, as shown in the diagram - HSC - SSCE Mathematics Advanced - Question 14 - 2024 - Paper 1

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The curves $y = (x - 1)^2$ and $y = 5 - x^2$ intersect at two points, as shown in the diagram. (a) Find the x-coordinates of the points of intersection of the two c... show full transcript

Worked Solution & Example Answer:The curves $y = (x - 1)^2$ and $y = 5 - x^2$ intersect at two points, as shown in the diagram - HSC - SSCE Mathematics Advanced - Question 14 - 2024 - Paper 1

Step 1

Find the x-coordinates of the points of intersection of the two curves.

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Answer

To find the points of intersection, set the equations equal:

(x1)2=5x2(x - 1)^2 = 5 - x^2

Expanding the left side gives:

x22x+1=5x2x^2 - 2x + 1 = 5 - x^2

Rearranging the equation leads to:

2x22x4=02x^2 - 2x - 4 = 0

Dividing by 2:

x2x2=0x^2 - x - 2 = 0

Factoring the quadratic equation, we get:

(x2)(x+1)=0(x - 2)(x + 1) = 0

Thus, the solutions for x are:

x=2,1x = 2, -1

Step 2

Find the area enclosed by the two curves.

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Answer

The area A between the curves can be calculated using the integral:

A=12[(5x2)(x1)2]dxA = \int_{-1}^{2} [(5 - x^2) - (x - 1)^2] \: dx

First, simplify the integrand:

5x2(x22x+1)=52x2+2x1=42x2+2x5 - x^2 - (x^2 - 2x + 1) = 5 - 2x^2 + 2x - 1 = 4 - 2x^2 + 2x

Now the integral becomes:

A=12(42x2+2x)dxA = \int_{-1}^{2} (4 - 2x^2 + 2x) \: dx

Calculating the integral:

=[4x23x3+x2]12 = \left[ 4x - \frac{2}{3}x^3 + x^2 \right]_{-1}^{2}

Evaluating at the limits:

=(4(2)23(23)+(22))(4(1)23(13)+(1)2) = \left( 4(2) - \frac{2}{3}(2^3) + (2^2) \right) - \left( 4(-1) - \frac{2}{3}(-1^3) + (-1)^2 \right)

=(8163+4)(4+23+1) = (8 - \frac{16}{3} + 4) - (-4 + \frac{2}{3} + 1)

Simplify:

=(12163)(3+23) = (12 - \frac{16}{3}) - (-3 + \frac{2}{3})

Combine:

=(12+316323)=39183=213=7 = \left( 12 + 3 - \frac{16}{3} - \frac{2}{3} \right) = \frac{39 - 18}{3} = \frac{21}{3} = 7

Thus, the area enclosed by the two curves is:

A=9A = 9

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