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Paper 1 Algebra. Leaving Certificate Helpdesk 20 th September 2012. General Content for Algebra. Simultaneous Equations Modulus Equations Inequalities The Nature of Roots of a Quadratic Equation Complex Numbers. Simultaneous Equations: Example 1. Solve the simultaneous equations:
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Paper 1Algebra Leaving Certificate Helpdesk 20th September 2012
General Content for Algebra • Simultaneous Equations • Modulus Equations • Inequalities • The Nature of Roots of a Quadratic Equation • Complex Numbers
Simultaneous Equations: Example 1 Solve the simultaneous equations: _______________________________________ Step 1: Eliminate one of the variables.
Step 2: Solve for either or using the following equations: Step 3: Solve for by subbing for in the equation:
Step 4: Solve for using one of the original equations. We know and Answers:
Simultaneous Equations in Three Variables Method: • Select one pair of equations and eliminate one of the variables. • Select another pair and eliminate the same variable. • Solve these two new equations simultaneously. • Use answers to find third variable.
Simultaneous Equations: Example 2 Solve the simultaneous equations
Simultaneous Equations: Example 3 2012 Paper 1 Q1(a)
Rational Inequalities Method: Turn the rational inequality into a quadratic inequality by multiplying both sides by a positive expression. Example: Solve the inequality Note: multiplying both sides by a squared value ensures that the inequality sign is not affected.
Solve the Quadratic to find the roots so that we can sketch the graph of the quadratic.
Roots: When is ? Answer:
Modulus Equations / Inequalities Solution: Square both sides
Solve the quadratic to find the roots and sketch the curve: Complete all multiplication and tidy up the expression:
Roots: Where is ? Answer: The inequality is true when
The Nature of Roots of a Quadratic Example: 2009 Question 2 (b)(i)
The Nature of Roots of a Quadratic Two real roots: Equal roots: Note: Roots are real if
The Nature of Roots of a Quadratic Imaginary Roots:
Quadratic Roots Example 1 The equation has equal roots. Find the possible values of k. Solution: Equal roots:
Quadratic Roots Example 2 Sample Paper 2012 Paper 1 Q3
If is a root then Conclusion: is a root of
If is a root then is a factor of Solution: Divide into
We now know: Solve to find final two roots Use
The real root must be as we are told at the start that Thus are the imaginary roots Therefore