Advertisements
Advertisements
Question
If a - b = 7 and ab = 18; find a + b.
Advertisements
Solution
We know that,
( a - b )2 = a2 - 2ab + b2
and
( a + b )2 = a2 + 2ab + b2
Rewrite the above equation, we have
( a + b )2 = a2 + b2 - 2ab + 4ab
= ( a + b )2 + 4ab ...(1)
Given that a - b = 7; ab = 18
Substitute the values of ( a - b ) and (ab)
in equation (1), we have
( a + b )2 = (7)2 + 4(18)
= 49 + 72 = 121
⇒ a + b = `+- sqrt121`
⇒ a + b = `+-11`
APPEARS IN
RELATED QUESTIONS
Evaluate the following using identities:
(1.5x2 − 0.3y2) (1.5x2 + 0.3y2)
Write in the expanded form:
`(m + 2n - 5p)^2`
Find the following product:
If \[x^2 + \frac{1}{x^2} = 102\], then \[x - \frac{1}{x}\] =
If \[3x + \frac{2}{x} = 7\] , then \[\left( 9 x^2 - \frac{4}{x^2} \right) =\]
Find the square of : 3a - 4b
Use identities to evaluate : (502)2
Evaluate : (4a +3b)2 - (4a - 3b)2 + 48ab.
Use the direct method to evaluate :
(2a+3) (2a−3)
Evaluate: (4 − ab) (8 + ab)
