If a – b = 7 and 2ab = 18 then a^2 + b^2 =

Question

A. 67
B. 49
C. 40
D. 31
E. 14

pushpitkc · Answer

Formula used :   (a-b)^2 = a^2 + b^2 - 2ab

Therefore,  a^2 + b^2 = (a-b)^2 +2ab 
Substituting values,
 a^2 + b^2 = (7)^2 +18 = 49 + 18 = 67 (Option A)

Arsh4MBA · Answer

a^2+b^2= (a-b)^2+2ab= 7^2+18=49+18=67
 Ans:A

JeffTargetTestPrep · Answer

We can square the first equation and we have:

(a – b)^2 = 7^2

a^2 - 2ab + b^2 = 49

Substituting 18 for 2ab, we have:

a^2 - 18 + b^2 = 49

a^2 + b^2 = 67

Answer: A

Pritishd · Answer

The key here is to recall the formula of  (a - b)^2  as soon as you look at equations such as  a - b = 7  and  2ab = 18 .

1. Now,  (a - b)^2 = a^2 + b^2 - 2ab 
2. Substituting  a - b = 7  and  2ab = 18  we get,  49 = a^2 + b^2 - 18 
3. Solving the above equation, we get  a^2 + b^2 = 67

Ans.  A

If a – b = 7 and 2ab = 18 then a^2 + b^2 =

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If a – b = 7 and 2ab = 18 then a^2 + b^2 =

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