Elitmus
Exam
Logical Reasoning
Direction Sense
(a-b)^2=25 and (a+b)^2=1,what is the value of a and b?
a)if a>0>b
b)a=2
Read Solution (Total 17)
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- after solving both eqq we get ab= -6
now from (2) we clearly get the value of (a,b)=(2,-3)
but from (1) ab= -6
(a,b)=(2,-3)/ (3,-2)
there are two possible set from statement (1).
therefore i think only statement 2 is required to ans. - 10 years agoHelpfull: Yes(14) No(11)
- both statements are required
- 10 years agoHelpfull: Yes(5) No(5)
- only (b) can give answer.
By solving these 2 equations we get values of {a,b} as {3,-2} or {-3,2} or {2,-3} or {-2,3}
from (a) we get the values for {a,b} as {3,-2} or {2,-3} , we didn't get single value for a or b thus we cannot answer what is the exact value of a or b.
from (b) we get {a,b}={2,-3}, thus we get values of a and b from condition (b) only. - 10 years agoHelpfull: Yes(3) No(0)
- both alone csn give the answer
(a-b)^2=a^2+b^2-2ab=25-----(1)
(a+b)^2=a^2+b^2+2ab=1-----(2)
(1)+(2)
2(a^2+b^2)=26
so there are 4 no ( +2,-2,-3,+3)
- 10 years agoHelpfull: Yes(2) No(8)
- Either of statements is sufficient.
(a-b)^2=25 means (a-b)=+5 or -5 and (a+b)^2=1 means (a+b)=+1 or -1..but acc to first statement (a-b)=5 and a-b=-1 are only possible values so by solving,a=2 and b=-3..
And acc to statement 2nd a=2 is given already. So either of the statements is sufficient. - 10 years agoHelpfull: Yes(2) No(0)
- it would be better if u will finalise one solution after discussion for any question....
- 9 years agoHelpfull: Yes(2) No(0)
- (a-b)^2=25 and (a+b)^2=1
a-b=5----------(1)
a-b=-5---------(2)
a+b=1 ---------(3)
a+b=-1 --------(4)
a)a>0, b - 10 years agoHelpfull: Yes(1) No(4)
- Here after making a square root then we get a+b=+1 or -1 & a-b=+5 or -5.
by solving these two equations we get a=-3,2 & b=2,-3.
So as per given condition if a=2, then b must be -3. - 10 years agoHelpfull: Yes(1) No(3)
- both alone csn give the answer
(a-b)^2=a^2+b^2-2ab=25-----(1)
(a+b)^2=a^2+b^2+2ab=1-----(2)
(1)+(2)
2(a^2+b^2)=26
a^2+b^2=13
put a=2 ucan easily find b
so b alone is sufficient to give answer
- 10 years agoHelpfull: Yes(1) No(0)
- (a-b)^2=25
then a-b=+5
and a-b=-5
so that
(a+b)=1
then
a+b=+1
and
a-b=-1
we take
a+b=-1
a-b=5
and solve it
we find the solution
a=2
b=-3
satisfy the condition given in question
- 9 years agoHelpfull: Yes(1) No(0)
- a^2+b^2-2ab=25
a^2+b^2+2ab=1
subtracting both equation
-4ab=24
ab=-6
a=2
b=-3 - 10 years agoHelpfull: Yes(0) No(5)
- (a-b)^2=25 and (a+b)^2=1
a-b=5----------(1)
a-b=-5---------(2)
a+b=1 ---------(3)
a+b=-1 --------(4)
a)a>0, b - 10 years agoHelpfull: Yes(0) No(3)
- Ans should be statement b, a=2
because if we solve the equation then we will get ab= -6,
now from statement a) we will get only range of value of a and b which will not give exact solution but
from statement b. we have exact value of a=2 from their we can get value of b easily and we can proof sat a) also.
but here we need only value of a and b so Statement b is sufficient to give answer. - 10 years agoHelpfull: Yes(0) No(0)
- Ans: Statement I
Sol : after solving above equation ,we get
four combination value for (a,b)
(2,3),(-2,3),(2,-3)and(-2,-3)
According condition I , we got
(2,-3)
- 9 years agoHelpfull: Yes(0) No(0)
- (a-b)^2= a^2 + b^2 -2ab = 25 ------1
(a+b)^2=a^2 + b^2 +2ab = 1 ------2
now sove the equation we got 2(a^2 + b^2)=26
a^2 + b^2= 13
a and b= 2 or 3
2^2 + 3^2= 13
4+9=13
or a and b -2 or -3
so both are correct any one are ok for ans
- 8 years agoHelpfull: Yes(0) No(0)
- a+b=+1,-1------(1)
a-b=+5,-5-------(2)
by solving both 1 & 2 we get
a= +3,-3 and b=+2,-2
so its satisfy to the 1 st option in the question "a)if a>0>b"
so ans is "a"
- 8 years agoHelpfull: Yes(0) No(0)
- Ans : using state I alone we can answer this question but using statement II alone ,
Solution:
using statement I
(a-b)^2=5; (a+b)^2=1
(a-b)=+ 5 or (a-b)= -5;
similarly (a+b)=+1 or (a+b)= -1
Solve the above equations..
since a >0>b the value of a and b should be greater than 0
hence we get definite value for a and b by using this statement ie a=3 , b=2
USING STATEMENT II
(a-b)^2=25
(a+b)^2=1
a^2+b^2-2ab=25
a^2+b^2+2ab=1
2(a^2+b^2)=26
a^2+b^2=13
substituting a=2
2^2+b^2=13
4+b^2=13
b^2=9
b=+ 3 or -3
here we do not get definite value of b , it could be 3 or -3 , so cannot be determined using statement II
- 8 years agoHelpfull: Yes(0) No(0)
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