8th Class Mathematics Sample Paper Mathematics Sample Paper - 3

  • question_answer If a + b = 25 and \[{{a}^{2}}+{{b}^{2}}=225,\]then find ab.

    Answer:

    We know that,
    \[{{\left( a+b \right)}^{2\text{ }}}=\text{ }{{a}^{2}}+{{b}^{2}}+2ab~~\]                                                                                                                          
    Here, \[a+b\text{ }=25,\text{ }{{a}^{2}}+{{b}^{2}}=225~~\]
    \[\Rightarrow \]   \[{{(25)}^{2}}=225+2ab\]                                                                                                                                                        
    \[\Rightarrow \]   625 = 225 + 2ab                                                                                                                                                                                      
    \[625-225=2ab\]                                                                                                                                                    
    \[\Rightarrow \,\] 400 = 2ab                                                                                                                                                            
    \[\Rightarrow \,\] \[ab=\frac{400}{2}\]
    \[\Rightarrow \,\]ab = 200


adversite


You need to login to perform this action.
You will be redirected in 3 sec spinner