1.

यदि `a+b=10` और `ab=21` हो तब `(a-b)^(2)` का मान ज्ञात करें?A. 15B. 16C. 17D. 18

Answer» Correct Answer - B
`a+b=10` and `ab=21`
`(a+b)=10`
`a^(2)+b^(2)+2ab=100`
`a^(2)+b^(2)=100-2ab`
`a^(2)+b^(2)=100-2xx21`
`=100-42`
`a^(2)+b^(2)=58`…………….i
`(a-b)^(2)=a^(2)+b^(2)-2ab`
`=58-2xx21`
from equation i
`=58-42`
`(a-b)^(2)=16`


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