Look at the simultaneous equations below.

[tex]
\begin{aligned}
y & = x + 6 \\
x^2 + y^2 & = 26
\end{aligned}
[/tex]

a) Show that [tex] x^2 + 6x + 5 = 0 [/tex]

b) Use part a) to solve the simultaneous equations. If any of your answers are decimals, give them to 1 d.p.



Answer :

Sure! Let's solve the given simultaneous equations step by step.

The given system of equations is:

1) [tex]\( y = x + 6 \)[/tex]
2) [tex]\( x^2 + y^2 = 26 \)[/tex]

Part (a): Show that [tex]\( x^2 + 6x + 5 = 0 \)[/tex]

To start, substitute [tex]\( y = x + 6 \)[/tex] from the first equation into the second equation.

[tex]\[ x^2 + (x + 6)^2 = 26 \][/tex]

Now, expand the squared term:

[tex]\[ x^2 + (x^2 + 12x + 36) = 26 \][/tex]

Combine like terms:

[tex]\[ x^2 + x^2 + 12x + 36 = 26 \][/tex]

Simplify the equation by combining the [tex]\( x^2 \)[/tex] terms and constant terms:

[tex]\[ 2x^2 + 12x + 36 = 26 \][/tex]

Move all terms to one side to set the equation to zero:

[tex]\[ 2x^2 + 12x + 36 - 26 = 0 \][/tex]

Simplify the constants:

[tex]\[ 2x^2 + 12x + 10 = 0 \][/tex]

Next, divide the entire equation by 2 for simplification:

[tex]\[ x^2 + 6x + 5 = 0 \][/tex]

This matches the required form, hence we have shown that:

[tex]\[ x^2 + 6x + 5 = 0 \][/tex]

Part (b): Use part (a) to solve the simultaneous equations

Now that we have [tex]\( x^2 + 6x + 5 = 0 \)[/tex], we can solve this quadratic equation.

The quadratic equation [tex]\( x^2 + 6x + 5 = 0 \)[/tex] can be factored as:

[tex]\[ (x + 1)(x + 5) = 0 \][/tex]

Setting each factor equal to zero gives the solutions for [tex]\( x \)[/tex]:

[tex]\[ x + 1 = 0 \implies x = -1 \][/tex]
[tex]\[ x + 5 = 0 \implies x = -5 \][/tex]

Now, substitute these [tex]\( x \)[/tex] values back into the equation [tex]\( y = x + 6 \)[/tex] to find the corresponding [tex]\( y \)[/tex] values.

For [tex]\( x = -1 \)[/tex]:

[tex]\[ y = -1 + 6 = 5 \][/tex]

For [tex]\( x = -5 \)[/tex]:

[tex]\[ y = -5 + 6 = 1 \][/tex]

Therefore, the solutions to the simultaneous equations are:

1. [tex]\( (x, y) = (-1, 5) \)[/tex]
2. [tex]\( (x, y) = (-5, 1) \)[/tex]

So, the pair of solutions for the simultaneous equations are:

1. [tex]\( (-5, 1) \)[/tex]
2. [tex]\( (-1, 5) \)[/tex]

No decimals were produced in this solution, so we are done.