If (x+1)(x-8)=0, what are the roots of the equation?
Answer and explanation
Correct answer: -1, 8
By the zero-product rule, if a product of two factors is zero then at least one factor must be zero. For (x+1)(x-8)=0 either x+1=0 or x-8=0. Solving gives x=-1 and x=8, so the roots are -1 and 8. The nearest distractor A (1, 8) has the sign of the first root wrong. Exam tip: set each factor to zero to find roots and substitute them back into the equation to verify quickly.
Frequently asked questions
What is the correct answer to this question?
-1, 8
Why is this the correct answer?
By the zero-product rule, if a product of two factors is zero then at least one factor must be zero. For (x+1)(x-8)=0 either x+1=0 or x-8=0. Solving gives x=-1 and x=8, so the roots are -1 and 8. The nearest distractor A (1, 8) has the sign of the first root wrong. Exam tip: set each factor to zero to find roots and substitute them back into the equation to verify quickly.
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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