InterviewSolution
Saved Bookmarks
| 1. |
Solve for `x(5+2sqrt(6))^x^(2-3)+(5-2sqrt(6))^x^(2-3)=10`(1985,5M) |
|
Answer» `(5+2sqrt(6))(5-2sqrt(6))=1` `:.(5-2sqrt(6))=1/((5+2sqrt(6)))` `:.(5+2sqrt(6))^(x^(2)-3)+(5-2sqrt(6))^(x^(2)-3)=10` reduces to `(5+2sqrt(6))^(x^(2)-3)+(1/(5+2sqrt(6))))^(x^(2)-3)=10` Put `(5+2sqrt(6))^(x^(2)-3)=t`, then `t+1/t=10` `impliest^(2)-10t+1=0` or `t=(10+-sqrt((100-4)))/2=(5+-2sqrt(6))` `implies(5+2sqrt(6))^(x^(2)-3)=(5+-2sqrt(6))=(5+2sqrt(6))^(+-1)` `:.x^(2)-3=+-1` `impliesx^(2)-3=1` or `x^(2)-3=-1` `impliesx^(2)=4` or `x^(2)=2` Hence `x=+-2, +-sqrt(2)`. |
|