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The point P divides the interval from A(−4, −4) to B(1, 6) internally in the ratio 2:3 - HSC - SSCE Mathematics Extension 1 - Question 11 - 2017 - Paper 1

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The point P divides the interval from A(−4, −4) to B(1, 6) internally in the ratio 2:3. Find the x-coordinate of P. (b) Differentiate tan⁻¹(x³). (c) Solve 2x/(x +... show full transcript

Worked Solution & Example Answer:The point P divides the interval from A(−4, −4) to B(1, 6) internally in the ratio 2:3 - HSC - SSCE Mathematics Extension 1 - Question 11 - 2017 - Paper 1

Step 1

Find the x-coordinate of P.

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Answer

To find the x-coordinate of point P, we use the section formula for internal division. The coordinates of A are (-4, -4) and B are (1, 6). The ratio is 2:3, which means:

Px=mx2+nx1m+n=21+3(4)2+3=2125=105=2.P_x = \frac{m \cdot x_2 + n \cdot x_1}{m + n} = \frac{2 \cdot 1 + 3 \cdot (-4)}{2 + 3} = \frac{2 - 12}{5} = \frac{-10}{5} = -2.

Thus, the x-coordinate of P is -2.

Step 2

Differentiate tan⁻¹(x³).

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Answer

Let ( y = \tan^{-1}(x^3) ).

Using the chain rule, the derivative is:

dydx=11+(x3)23x2=3x21+x6.\frac{dy}{dx} = \frac{1}{1 + (x^3)^2} \cdot 3x^2 = \frac{3x^2}{1 + x^6}.

Step 3

Solve 2x/(x + 1) > 1.

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Answer

To solve the inequality:

  1. Multiply both sides by (x + 1) (noting that this changes the inequality if x + 1 < 0):  2x>x+1.\ 2x > x + 1.
  2. Rearranging gives us:  2xx>1    x>1.\ 2x - x > 1 \implies x > 1.
  3. Consider the case when (x + 1) < 0, so ( x < -1 ):  2x<x+1    x<1.\ 2x < x + 1 \implies x < 1.
  4. Therefore, the solution is:  x>1 or x<1.\ x > 1 \text{ or } x < -1.

Step 4

Sketch the graph of the function y = 2 cos⁻¹(x).

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Answer

The graph of ( y = 2 \cos^{-1}(x) ) is between the points x = -1 and x = 1. The range of y is between 0 and 2π. At x = -1, y = 2π and at x = 1, y = 0. The graph is a decreasing function, falling from (0, 2π) to (1, 0), creating a concave shape.

Step 5

Evaluate \( \int_{0}^{3} \frac{x}{\sqrt{x + 1}} \, dx \), using the substitution x = u² − 1.

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Answer

  1. Let ( x = u^2 - 1 ) then ( dx = 2u , du. )
  2. The limits change: when x = 0, u = 1, and when x = 3, u = 2.
  3. Substitute into the integral:
12u21u2(2udu)=212(u21)du=2[u33u]12.\int_{1}^{2} \frac{u^2 - 1}{\sqrt{u^2}} (2u \, du) = 2\int_{1}^{2} (u^2 - 1) \, du = 2\left[ \frac{u^3}{3} - u \right]_{1}^{2}.
  1. Calculate:
=2(832(131))=2(86+13)=2(33)=2.= 2\left(\frac{8}{3} - 2 - \left(\frac{1}{3} - 1\right)\right) = 2\left(\frac{8 - 6 + 1}{3}\right) = 2 \left( \frac{3}{3} \right) = 2.

Step 6

Find \( \int \sin^{2}(x) \, \cos(x) \, dx. \)

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Answer

Using the substitution ( u = \sin(x), ; du = \cos(x) , dx. )

The integral becomes:

u2du=u33+C=sin3(x)3+C.\int u^2 \, du = \frac{u^3}{3} + C = \frac{\sin^3(x)}{3} + C.

Step 7

Write an expression for the probability that exactly three of the eight seedlings produce red flowers.

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Answer

Let ( p = \frac{1}{5} ) and ( q = \frac{4}{5} ). The required probability is given by the binomial formula:

P(X=3)=(83)p3q5=(83)(15)3(45)5.P(X = 3) = \binom{8}{3} p^3 q^{5} = \binom{8}{3} \left(\frac{1}{5}\right)^{3} \left(\frac{4}{5}\right)^{5}.

Step 8

Write an expression for the probability that none of the eight seedlings produces red flowers.

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Answer

The probability that none produces red flowers is given by:

P(X=0)=(80)p0q8=(45)8.P(X = 0) = \binom{8}{0} p^0 q^{8} = \left(\frac{4}{5}\right)^{8}.

Step 9

Write an expression for the probability that at least one of the eight seedlings produces red flowers.

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Answer

The probability that at least one seedling produces red flowers is the complement of none:

P(X1)=1P(X=0)=1(45)8.P(X \geq 1) = 1 - P(X = 0) = 1 - \left(\frac{4}{5}\right)^{8}.

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