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Question 14 (a) (i) Factorise $x^2 + 6x - 7$ - Junior Cycle Mathematics - Question 14 - 2016

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Question 14 (a) (i) Factorise $x^2 + 6x - 7$. $x^2 + 6x - 7 = (x + 7)(x + )$ (ii) Using the factors from part (a) (i), or otherwise, solve the equation: $x^2 + ... show full transcript

Worked Solution & Example Answer:Question 14 (a) (i) Factorise $x^2 + 6x - 7$ - Junior Cycle Mathematics - Question 14 - 2016

Step 1

Factorise $x^2 + 6x - 7$

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Answer

To factorise the quadratic expression x2+6x7x^2 + 6x - 7, we need to find two numbers that multiply to -7 (the constant term) and add up to 6 (the coefficient of the linear term). The numbers 7 and -1 satisfy this condition.

Thus, we can write: x2+6x7=(x+7)(x1)x^2 + 6x - 7 = (x + 7)(x - 1)

Step 2

Using the factors from part (a) (i), or otherwise, solve the equation: $x^2 + 6x - 7 = 0$

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Answer

Now, using the factors previously found, we can set each factor to zero:

  1. From (x+7)=0(x + 7) = 0: x=7x = -7

  2. From (x1)=0(x - 1) = 0: x=1x = 1

Therefore, the solutions to the equation x2+6x7=0x^2 + 6x - 7 = 0 are: x=7 extandx=1x = -7\ ext{ and } x = 1

Step 3

Solve the following simultaneous equations: $3x + 2y = 39$ and $x + 2y = 25$

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To solve the simultaneous equations, we can start with the second equation:

x+2y=25    x=252yx + 2y = 25 \implies x = 25 - 2y

Next, we can substitute this expression for xx into the first equation:

3(252y)+2y=393(25 - 2y) + 2y = 39

Expanding this gives: 756y+2y=3975 - 6y + 2y = 39

Combining like terms results in: 754y=3975 - 4y = 39

Now, isolating yy: 4y=3975-4y = 39 - 75 4y=36-4y = -36 y=9y = 9

Now substituting y=9y = 9 back into x=252yx = 25 - 2y: x=252(9)=2518=7x = 25 - 2(9) = 25 - 18 = 7

Thus, the solution to the simultaneous equations is: x=7 extandy=9x = 7\ ext{ and } y = 9

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