solve it pls

乖学生

1. If a^(1/2) - a^(-1/2)= 1, prove that a + a^(-1) = 3
2. By means the substitution y = 2^x, find the values of x which satisfy the equation
                     2^(2x+3) = 11(2^(x+2)) - 9

HanQing

well i din use the substitution of y, hope it helps

乖学生

回复 2# HanQing


    the 1st ques if i use the method like tat can onot?

                   a^(1/2) - a^(-1/2)=1  ... all term times ^2
                    a - a^-1=1

HanQing

回复 3# 乖学生

It's not right to do so =/ and it's wrong

Taking an example,

1+2 = 3

If i were to square each of the number as you proposed earlier, it would end up like this

1^2+2^2 =3^2
1+4 =9 [ well, it's obvious the RHS is not equivalent to LHS ]

What if  i square both side
(1+2)^2 = 3^2
3^2=3^2  [ RHS=LHS]

乖学生

回复 4# HanQing

so, is it means tat if wan times ^2 nid apply to both side whole equation?
                  <LHS>^2=<RHS>^2

HanQing

回复 5# 乖学生


    that's right.

乖学生

回复 6# HanQing


    OK,thx...
u got msn??i wan ask u if i face trouble....

HanQing

回复 7# 乖学生


    would be glad if i can help you solving your problems, but now i am still waiting for lower six admission and maybe i am unable to answer higher level questions =/ What about post out your questions here so that those notable maths experts here might try it out and help you instead? =)

iamverynoob

楼上的两位，请用中文回复

HanQing

好的,抱歉