Mathematics
NULL
Medium
Question
If a and b are the roots of x² − 9x + 20 = 0, find the value of a² + b² + ab.
A
-21
B
1
C
61
✓ Official correct answer
D
21
Community credibility
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A
-21
No member explanations yet for this option.
B
1
No member explanations yet for this option.
C
61
No member explanations yet for this option.
D
21
No member explanations yet for this option.
Explanation
a + b = 9, ab = 20. a² + b² + ab = (a+b)² − ab = 81 − 20 = 61.