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Factorise $x^2 + 4x - 5$ - Junior Cycle Mathematics - Question 11 - 2017

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Question 11

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Factorise $x^2 + 4x - 5$. One of the factors is $(x + 5)$. $$x^2 + 4x - 5 = (x + 5)( \, )$$ Using your factors from part (a), or otherwise, solve the equation: $x... show full transcript

Worked Solution & Example Answer:Factorise $x^2 + 4x - 5$ - Junior Cycle Mathematics - Question 11 - 2017

Step 1

Factorise $x^2 + 4x - 5$

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Answer

To factor the quadratic expression x2+4x5x^2 + 4x - 5, we are given that one of the factors is (x+5)(x + 5). We can represent the expression in factorised form as:

x2+4x5=(x+5)(x1)x^2 + 4x - 5 = (x + 5)(x - 1).

This is derived by finding a pair of numbers that multiply to 5-5 (the constant term) and add to 44 (the coefficient of xx). The numbers are 55 and 1-1.

Step 2

Using your factors from part (a), or otherwise, solve the equation: $x^2 + 4x - 5 = 0$

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Answer

Using the factored form (x+5)(x1)=0(x + 5)(x - 1) = 0, we can set each factor equal to zero:

  1. x+5=0x + 5 = 0 implies that x=5x = -5.
  2. x1=0x - 1 = 0 implies that x=1x = 1.

Thus, the solutions are x=5x = -5 and x=1x = 1.

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