1) the average of four positive numbers is 15. The second number is 2 times the first number. The third number is twice the second. The last number is the last square of the first number. what is the largest number?

Question

2) suppose that 4x^2 + 8xy +4xy^2=576. If x is greater than 1and y is greater than 1.What is the largest number that x could be if x is divisible by y?

3) find the square root of (a^2)/(b^2) + (a^2)/(b^2)

Answer 1

#1.
Let x be the smallest. Then we know that
(x + 2x + 2*2x + x^2)/4 = 15
find x, then x^2

#2
4x^2 + 8xy +4xy^2=576
x^2 + 2xy + xy^2 = 144
If x=12, y = -2
So, x must be one of 1,2,3,4,6
I don't see any integer solutions with x,y > 1

#3
(a^2)/(b^2) + (a^2)/(b^2)
= (a^2+a^2)/b^2
= 2a^2/b^2
so, the square root is (a/b)√2

Answer 2

For number 1 I solved it and got x^2= 25?

Can number 3 be written as = a radical 2 over b?