# U-Substitution

#### noahpww

##### New member
Hello Everybody,

I'm really struggling with this following 3-part problem. Any help or guidance through them would be greatly appreciated.

1a. Using u-substitution, solve (x^2 - 2)^2 - 3(x^2 - 2) - 4 = 0.

So I was able to figure this problem out using u-substitution and got x = (±) square root of 6 & x = ±1.

1b. The quadratic formula solves equations of the form ax^2 + bx + c = 0. Find the formula that solves a(x^2 - d)^2 + b(x^2 - d) + c = 0

For this problem, their looking for a formula but I'm not sure which one or how to find it.

For this last part, part 1b must be completed.

#### Subhotosh Khan

##### Super Moderator
Staff member
Hello Everybody,

I'm really struggling with this following 3-part problem. Any help or guidance through them would be greatly appreciated.

1a. Using u-substitution, solve (x^2 - 2)^2 - 3(x^2 - 2) - 4 = 0. use u = x^2 - 2

So I was able to figure this problem out using u-substitution and got x = (±) square root of 6 & x = ±1.

1b. The quadratic formula solves equations of the form ax^2 + bx + c = 0. Find the formula that solves a(x^2 - d)^2 + b(x^2 - d) + c = 0

For this problem, their looking for a formula but I'm not sure which one or how to find it. use u = x^2 - d

For this last part, part 1b must be completed.
.

#### Jomo

##### Elite Member
Hello Everybody,

I'm struggling with this 3-part problem. Any help or suggestions would be greatly appreciated!

1a. Using u-substitution, solve (x^2 - 2)^2 - 3(x^2 - 2) - 4 = 0.

I was able to solve this problem using u-substitution and got x = (±) the square root of 6 & x = ±1. You really should say which substitution you made since if you made a mistake we would not be able to help you. Having said that, you used u=x2-2 and got the correct answers. Good for you.

1b. The quadratic formula solves equations of the form ax^2 + bx + c = 0. Find the formula that solves a(x^2 - d)^2 + b(x^2 - d) + c = 0. Let u = x2-d and do exactly what you did above. You'll have d instead of 2

This one asks for a formula but I'm not sure which one and how to find it.