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- If a and b are the roots of the equation x² - 9x + 20 = 0, find the value of a² + b² + ab?
Question 1:
If a and b are the roots of the equation x² - 9x + 20 = 0, find the value of a² + b² + ab? A. -21
B. 1
C. 61
Feedback a² + b² + ab = a² + b² + 2ab - ab
i.e., (a + b)² - ab
from x² - 9x + 20 = 0, we have a + b = 9 and ab = 20. Hence the value of required expression (9)² - 20 = 61.
i.e., (a + b)² - ab
from x² - 9x + 20 = 0, we have a + b = 9 and ab = 20. Hence the value of required expression (9)² - 20 = 61.
D. 21
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