Question

If (a+b) =5 and ab =2, find the value of (a2+b2).

Answer 1

Answer:

a²+b²=21

Step-by-step explanation:

Given,

(a+b)=5

ab=2

a²+b²=?

(a+b)²=a²+2ab+b²

(5)²=a²+2(2)+b²

25=a²+4+b²

25-4=a²+b²

21=a²+b²

a²+b²=21

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Answer 2

${(x + y)}^{2} = {x}^{2} + {y}^{2} + 2xy \\ \\ {x}^{2} + {y}^{2} = {(x + y)}^{2} - 2xy \\ \\ = {5}^{2} - 2 \times 2 \\ \\ = 25 - 4 \\ \\ = 21$