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Given that $x^2 - 6x + 1 = (x - a)^2 - b$ for all values of $x$, (i) find the value of $a$ and the value of $b$ - Edexcel - GCSE Maths - Question 20 - 2019 - Paper 1

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Given-that---$x^2---6x-+-1-=-(x---a)^2---b$---for-all-values-of-$x$,---(i)-find-the-value-of-$a$-and-the-value-of-$b$-Edexcel-GCSE Maths-Question 20-2019-Paper 1.png

Given that $x^2 - 6x + 1 = (x - a)^2 - b$ for all values of $x$, (i) find the value of $a$ and the value of $b$. $a = $ $b = $ (2) (ii) Hence w... show full transcript

Worked Solution & Example Answer:Given that $x^2 - 6x + 1 = (x - a)^2 - b$ for all values of $x$, (i) find the value of $a$ and the value of $b$ - Edexcel - GCSE Maths - Question 20 - 2019 - Paper 1

Step 1

find the value of $a$ and the value of $b$

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Answer

To solve for aa and bb, we start by expanding the right-hand side of the equation:

(xa)2b=x22ax+a2b.(x - a)^2 - b = x^2 - 2ax + a^2 - b.

Next, we set the equations equal to each other:

x26x+1=x22ax+(a2b).x^2 - 6x + 1 = x^2 - 2ax + (a^2 - b).

By comparing coefficients, we can derive the following equations:

  1. The coefficient of xx:
    6=2aa=3.-6 = -2a \Rightarrow a = 3.

  2. The constant term:
    1=a2b1=32b1=9bb=8.1 = a^2 - b \Rightarrow 1 = 3^2 - b \Rightarrow 1 = 9 - b \Rightarrow b = 8.

Thus, the values are:

a=3a = 3 and b=8b = 8.

Step 2

Hence write down the coordinates of the turning point on the graph of $y = x^2 - 6x + 1$

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Answer

To find the coordinates of the turning point, we can use the vertex formula for a quadratic equation of the form y=ax2+bx+cy = ax^2 + bx + c. The xx-coordinate of the vertex is given by:

x=b2a.x = -\frac{b}{2a}.

In our case, a=1a = 1 and b=6b = -6, so:

x=62(1)=3.x = -\frac{-6}{2(1)} = 3.

We then substitute x=3x = 3 back into the original equation to find the yy-coordinate:

y=(3)26(3)+1=918+1=8.y = (3)^2 - 6(3) + 1 = 9 - 18 + 1 = -8.

Therefore, the coordinates of the turning point are:

(3,8)(3, -8).

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