Question

a+b=7, ab=18
find a–b
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Answer 1

Answer:

a+b = 7

a = 7-b

Substitute a in ab = 18

(7-b)(b) = 18

7b+b²-18 = 0

b²+7b-18 = 0

b²+9b-2b-18 = 0

b(b+9)-2(b+9) = 0

(b-2)(b+9) = 0

Either b-2 = 0 or b+9 = 0

b = 2 or -9

We will consider positive values,

So if b= 2 , a= 7-2 = 5

a-b = 5-2 = 3