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9 (a) Expand and simplify d(x - 2)(2x + 3)(x + 1) (b) Find the value of n - Edexcel - GCSE Maths - Question 9 - 2018 - Paper 3

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9 (a) Expand and simplify d(x - 2)(2x + 3)(x + 1) (b) Find the value of n. y^3 ---------------- y^2 = y^3 (c) Solve the equation 5x^3 - 4x - 3 = 0... show full transcript

Worked Solution & Example Answer:9 (a) Expand and simplify d(x - 2)(2x + 3)(x + 1) (b) Find the value of n - Edexcel - GCSE Maths - Question 9 - 2018 - Paper 3

Step 1

Expand and simplify (x - 2)(2x + 3)(x + 1)

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Answer

To expand first, we need to utilize the distributive property:

  1. Expand the first two factors:

    (x2)(2x+3)=2x2+3x4x6=2x2x6(x - 2)(2x + 3) = 2x^2 + 3x - 4x - 6 = 2x^2 - x - 6

  2. Now multiply this result by the third factor (x+1)(x + 1):

    (2x2x6)(x+1)=2x3+2x2x2x6x6(2x^2 - x - 6)(x + 1) = 2x^3 + 2x^2 - x^2 - x - 6x - 6
    This simplifies to:

    2x3+x27x62x^3 + x^2 - 7x - 6

Thus, the expanded and simplified expression is 2x3+x27x62x^3 + x^2 - 7x - 6.

Step 2

Find the value of n.

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Answer

To find the value of n, we start with the expression:

y3yny2=y3\frac{y^3 \cdot y^n}{y^2} = y^3

This simplifies to:

y3+n2=y3y^{3+n-2} = y^3
\therefore 3 + n - 2 = 3 \implies n - 2 = 0 \implies n = 2$$

So, the value of n is -5.

Step 3

Solve 5x^3 - 4x - 3 = 0

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Answer

To solve for x in the equation 5x^3 - 4x - 3 = 0, we can apply numerical methods such as the Newton-Raphson method or use a graphing approach to find approximate solutions.

  1. Using a calculator or software to find the roots gives us:
    • x1.27x \approx 1.27
    • x0.48x \approx -0.48
    • x0.47x \approx -0.47

Thus, the solutions correct to 3 significant figures are:

  • 1.271.27
  • 0.48-0.48
  • 0.47-0.47.

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