If calphac and cbetac are the roots of cx^2-7x+10=0c, what is the value of (alpha-1)(beta-1)c?
Answer and explanation
Correct answer: 4
For a quadratic equation cax^2+bx+c=0c, the sum of the roots is alpha+beta=-b/ac and their product is alphabeta=c/ac. Hence, here alpha+beta=7c and alphabeta=10c. Therefore, (alpha-1)(beta-1)=alphabeta-alpha-beta+1=10-7+1=4c. Exam tip: For expressions involving roots, first find their sum and product instead of solving for the roots individually.
Frequently asked questions
What is the correct answer to this question?
4
Why is this the correct answer?
For a quadratic equation cax^2+bx+c=0c, the sum of the roots is alpha+beta=-b/ac and their product is alphabeta=c/ac. Hence, here alpha+beta=7c and alphabeta=10c. Therefore, (alpha-1)(beta-1)=alphabeta-alpha-beta+1=10-7+1=4c. Exam tip: For expressions involving roots, first find their sum and product instead of solving for the roots individually.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Quadratic Equations. Topic: Roots of a Quadratic Equation.
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