PSAT Math Grid-Ins Question 100: Answer and Explanation
Question: 100
The x-intercepts of the equation y = x2 - 9x + 20 are m and n, where m > n. What is the value of m?
Correct Answer: 5
Explanation:
5
Difficulty: Easy
Category: Solving Quadratics by Factoring
Getting to the Answer: Factor the given quadratic by finding factors of 20 that add, or subtract, to get the middle constant 9. Notice that -4 and -5 will multiply to get 20 and add to get -9. So, x2 - 9x + 20 = (x - 4)(x - 5). Set both equal to 0 and solve for x to get x = 4 and x = 5. Remember that the question asks for m, where m > n, or in other words for the larger of the two roots, so grid in 5.
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