Question

if a-b = 7 and ab=18 find a+b

Answer 1

a-b = 7 ...(i)And; ab = 18 ...(ii)Squaring both sides of (i) we get;a-b2 = 72⇒a2+b2-2ab = 49⇒a2+b2-2×18 = 49    {using (ii)}⇒a2+b2= 49+36⇒a2+b2 = 85⇒a+b2-2ab = 85         {Since; a2+b2 = a+b2-2ab }⇒a+b2-2×18 = 85         {using (ii)}⇒a+b2 = 121 ⇒a+b = 121 = 11

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Answer 2

Hey ur answer is here

We have two eq
A-b=7(1)
Ab=18(2)

There are other methods to solve this but I am using substitution method

We get a - b=7,a=7+b

Now put the value of a=7+b in (2)

Ab=18
(7+b)+b=18
B^2+b-18=0
Factories

B^2+9b-2b-18=0
B(b+9)-2(b+9)=0
( B-2)(b+9)=0
B=2,b=-9=0

So now b=2

Now put the value of b=2 in eq (1)
A=b+7=2+7=9

A=9&b=2
A+b=9+2=11

Hope it's help you friend ☺️☺️