The value of the expression (a - b)² from the given equations is; 16
We are given the two equations as;
a + b = 10 -----(eq 1)
ab = 21 ------(eq 2)
From eq 1, square both sides;
(a + b)² = 10²
a² + 2ab + b² = 100
a² + b² = 100 - 2ab
We are given ab = 21. Thus;
a² + b² = 100 - 2(21)
a² + b² = 58
Now, we know that (a - b)² = a² - 2ab + b²
Thus;
(a - b)² = 58 - 2(21)
(a - b)² = 16
Complete question is;
If a + b = 10 and ab = 21, then the value of (a - b)² is?
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