Solving Quadratic Identities: 2x^2 + 7x - 5 = A(x-1)^2 + Bx + C

In summary, the conversation is about solving the equation 2x^2 + 7x - 5 = A(x-1)^2 + Bx + C, with the goal of finding the values of A, B, and C. The suggested method is to substitute different values for x and create equations to solve for the unknowns. The final solution is A=2, B=11, and C=-7. The conversation also mentions helpful resources for solving similar equations.
  • #1
zebra1707
107
0

Homework Statement



2x^2 + 7x - 5 = A(x-1)^2 + Bx + C



Homework Equations



N/a

The Attempt at a Solution



This is an interesting equation as regardless of the whether I substitute x = 0 or x = 1 i still encounter the problem of not be able to make the calculation any easier. I have not been able to find any examples for guidence. Can someone assist.

Cheers
 
Last edited:
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  • #2
That's just an equation. What's the actual problem? Are you supposed to find A, B, and C given the equation is true for all x? That's just a guess.
 
  • #3
yes, sorry - need to find A, B and C

Cheers


Dick said:
That's just an equation. What's the actual problem? Are you supposed to find A, B, and C given the equation is true for all x? That's just a guess.
 
  • #4
Ok, then if ax^2+bx+c=0 for all x then a=0 and b=0 and c=0. Expand everything and move everything to one side. Set the coefficients of powers of x to zero and solve for A, B and C.
 
  • #5
Or do exactly what you suggested in your original post.

If x= 0, this becomes -5= A+ C. If x= 1, this becomes 4= B+ C. Since there are three unknown numbers, you need a third equation: If x= -1, this becomes -10= 4A- B+ C. Three equations to solve for A, B, and C. From equation one, A= -5-C. From equation 2, B= 4- C. Replace A and B with those in the third equation and solve for C.
 
  • #6
I ended up with A=2, B=11 and C= -7

Substituting the figures into the equation - it balances with the R.H.S.

I think that I have solved it - but happy for comment if I have it wrong.

Cheers
 
  • #7
A(x-1)2 + Bx + C = Ax2 + (B-2A)x + A+C

So at least A=2 is obviously OK, then A+C=2+C=-5, so C=-7. B-2A=B-4=7, so B is OK too.

--
methods
 
  • #8

Related to Solving Quadratic Identities: 2x^2 + 7x - 5 = A(x-1)^2 + Bx + C

1. What is the purpose of solving quadratic identities?

The purpose of solving quadratic identities is to find the values of the unknown variables (A, B, and C) in the equation that satisfies the given conditions. This helps in understanding the behavior and properties of quadratic equations and can be used to solve real-world problems.

2. How do you solve quadratic identities?

To solve quadratic identities, the first step is to simplify the equation using algebraic techniques such as factoring or the quadratic formula. Then, equate the coefficients of each term to the corresponding terms on the other side of the equation. Finally, solve the resulting system of equations to find the values of A, B, and C.

3. What is the difference between a quadratic identity and a quadratic equation?

A quadratic identity is an equation that is always true for any value of the variable, while a quadratic equation has a specific solution for the variable. In other words, a quadratic identity is an equation that is true for all values of x, whereas a quadratic equation has a finite set of solutions.

4. Can quadratic identities have complex solutions?

Yes, quadratic identities can have complex solutions. This occurs when the discriminant (b^2-4ac) is negative, resulting in complex roots. Complex solutions are represented in the form of a+bi, where a and b are real numbers and i is the imaginary unit.

5. How are quadratic identities used in real life?

Quadratic identities have various applications in real life, such as in physics, engineering, economics, and computer graphics. They can be used to model and analyze physical phenomena, optimize systems, predict trends in data, and create computer-generated images.

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