Question

Solve:

(u + 3)(u - 3) = 8u

Answer 1

u^2 - 9 = 8u
u^2 -8u -9=0
u^2 - 9u + u -9=0

Answer 2

now solve it like i did

Answer 3

I got u = 0; u = -3; u = 3

Answer 4

?

Answer 5

youll get only 2 values

Answer 6

u = -1; u = 9

Answer 7

now ur right

Answer 8

sorry I totally mess the first one up

Answer 9

Thanks !!!

Answer 10

using the fomula (a+b) (a-b) = a^2 - b^2 u get
u^2 - (3)^2 = 8u
=> u^2 - 8u - 9 = 0

now u hv to factorise -9 into two factors A and B so that AB = -9 and A + B = -8

9 * -1 = -9 and 9 + (-1) = 8

=> u^2 -9u + u - 9 =0
=> u(u-9) +1(u-9) = 0
=> (u+1) (u-9) = 0
for the product to b zero either of the factors has to b zero
if u+1 = 0 => u = -1
if u-9 = 0 => u = 9