Mathematics problems

danial
By danial

Can you please help me to solve this problem,
4a²+b² If 2a+b =3 and ab=1
Thanks.

By blackbeard• 13 Nov 2008 15:31
blackbeard

ohhh... I never thought I could post my homeworks here.. hmmm what can I ask, I'm having difficulty with my Calculus.. ^_^

By danial• 13 Nov 2008 15:07
danial

Hello,

Thanks all of you for helping me,

again thanks

By anonymous• 13 Nov 2008 08:06
Rating: 5/5
anonymous

Annez I guess has done it the correct way..

By annez• 13 Nov 2008 05:34
Rating: 5/5
annez

4a²+b² If 2a+b =3 and ab=1

(2a+b)² =4a²+b²+4ab

4a²+b²=(2a+b) ² -4ab

=(3) ² -4x1

=9-4

=5

By Shegoo• 12 Nov 2008 23:10
Rating: 4/5
Shegoo

ANSWER = 5

By lobo79• 12 Nov 2008 22:47
Rating: 5/5
lobo79

ab=1 then a=1/b

then the equation 2a+b=3 gives 2/b+b=3 then 2+bsquare=3

3b-bsquare=2 then b(3-b)=2 and now u have 2 answers for b are b=2 and

3-b=2 then -b=2-3 b=1

if b=2 then ab=1 it gives a*2=1 then a=1/2

the equation 4a2+b2=(1/4)*1+(4)=17

if b=1 then ab=1 it gives a*1=1 then a=1

the equation 4a2+b2=(4*1)+1=5

hope it is helpfull for you.

By wizmotr• 12 Nov 2008 22:44
Rating: 5/5
wizmotr

The answer is 5:

Given: ab=1 a=1/b (eq. 1)

Given: 2a+b=3 and substituting for a from eq. 1:

2a+b=3 2/b+b=3 (eq. 2)

Multiply eq. 2 by b: b(2/b+b)=3b 2+b^2=3b or

b^2-3b+2=0 (eq. 3)

Factoring eq. 3 results in: (b-2)(b-1)=0

By the laws of multiplication, either b-2=0 or b-1=0

Therefore b=2 or b=1

If b=2: a(2)=1 so a=1/2 and 4a^2+b^2 = 4(1/2)^2*2^2 = 5

If b=1: a(1) = 1 so a=1 and 4a^2+b^2 = 4(1)^2*1^2 = 5

So do I get a prize for doing your homework?

By Elusive• 12 Nov 2008 22:33
Rating: 2/5
Elusive

4a²+b²= (2a+b)(2a+b)= 4a²+2ab+2ab+b²

now substitue and do the calculations!!!

By GodFather.• 12 Nov 2008 22:23
GodFather.

answer is 9+2=11, I think

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