Find the range of values of $x$ for which $|x - 4| \geq 2$, where $x \in \mathbb{R}$ - Leaving Cert Mathematics - Question 2 - 2016
Question 2
Find the range of values of $x$ for which $|x - 4| \geq 2$, where $x \in \mathbb{R}$.
Solve the simultaneous equations:
$$x^2 + xy + 2y^2 = 4$$
$$2x + 3y = -1.$$
Worked Solution & Example Answer:Find the range of values of $x$ for which $|x - 4| \geq 2$, where $x \in \mathbb{R}$ - Leaving Cert Mathematics - Question 2 - 2016
Step 1
Find the range of values of $x$ for which $|x - 4| \geq 2$
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Answer
To solve the inequality ∣x−4∣≥2, we can break it into two cases:
Case 1: x−4≥2
Solving this gives: x≥6
Case 2: x−4≤−2
Solving this gives: x≤2
Combining these two cases, we find the range of values for x: x∈(−∞,2]∪[6,+∞).
Step 2
Solve the simultaneous equations: $x^2 + xy + 2y^2 = 4$ and $2x + 3y = -1$
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Answer
We can solve these equations by substitution or elimination. We'll use substitution:
From the second equation, express x: x=−23y+1
Substitute this into the first equation: (−23y+1)2+(−23y+1)y+2y2=4
Expanding this gives:
4(3y+1)2−2(3y+1)y+2y2=4
In clearing the fractions by multiplying through by 4, we get: 4(3y+1)2−2(3y+1)y+8y2=16
Continuing simplifies this down to a quadratic equation in y, which can be solved to find the values of y. From this, we can find corresponding x values.
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