how do u get 48y , and the 15 would that be 17-2?

Question

2x^2 - 9y^2 = 17
2(3y + 4)^2 - 9y^2 = 17
9y^2 + 48y + 15 = 0
3y^2 + 16y + 5 = 0
3y^2 + 15y + y + 5 = 0
3y(y +5) + 1(y + 5) = 0
(y + 5)(3y + 1) = 0
y = -5 and y = -1/3

x = 3y + 4
y = -5, x = - 11
y = -1/3, x = 3
The answer is correct, i just have to figure out the workings

Answer 1

From your second line:

When you expand (3y +4)^2 = 9y^2 + 24y + 16...then you must mulitply by the 2 out front...

18y^2 + 48y + 32 - 9y^2 = 17
9y^2 + 48y + 32 - 17 = 0
9y^2 + 48y + 15 = 0

Answer 2

its not too difficult :i think u should take some good classes about simplification

actually u missed the step which is after urs 2nd step

which is
2(9y^2+24y+16)-9y^2-17=0

then just multiply this 2 to the term in bracket
18y^2-48y+32-9y^2-17=0

9y^2+48y+15=0

3y^2+16y+15=0

u can proceed after that