Solve For A And B: $\frac{3}{x}+\frac{5}{x^2}=\frac{a X+b}{x^2}$

by Andrew McMorgan 65 views

Hey math whizzes! Ever feel like some equations just have missing pieces, like a puzzle waiting to be solved? Well, today we're diving into one of those! We've got this expression here: 3x+5x2=ax+bx2\frac{3}{x}+\frac{5}{x^2}=\frac{a x+b}{x^2}. Our mission, should we choose to accept it, is to find the values for 'a' and 'b' that make this equation a perfect match. It's a bit like being a detective, looking for clues to crack the case. This isn't just about plugging in numbers; it's about understanding how fractions work together and how we can combine them to achieve a specific form. So, grab your thinking caps, guys, because we're about to break this down step-by-step. We'll explore the fundamental principles of adding fractions with different denominators and how to manipulate them to find those elusive unknown values. Get ready to flex those mathematical muscles!

Understanding the Goal: Combining Fractions

Alright, team, let's get down to business. The core of this problem is adding fractions, but not just any fractions – fractions with different denominators. Remember back in the day when you learned that to add fractions, they must have the same bottom number, the denominator? This is exactly that principle in action, but with a little twist. Our left side has 3x\frac{3}{x} and 5x2\frac{5}{x^2}. Notice that the denominators are xx and x2x^2. To add these bad boys, we need a common denominator. Think of it like needing matching socks before you can go out – they just have to be the same! The least common denominator (LCD) here is pretty straightforward: it's x2x^2. Why x2x^2? Because x2x^2 is the smallest expression that both xx and x2x^2 can divide into evenly. So, our first move is to rewrite 3x\frac{3}{x} so it has a denominator of x2x^2. To do this, we multiply both the numerator and the denominator by xx. This is a super important trick: multiplying by xx\frac{x}{x} is like multiplying by 1, so it doesn't change the value of the fraction, just its appearance. So, 3x\frac{3}{x} becomes 3Γ—xxΓ—x\frac{3 \times x}{x \times x}, which simplifies to 3xx2\frac{3x}{x^2}. Now, our original equation looks like this: 3xx2+5x2=ax+bx2\frac{3x}{x^2} + \frac{5}{x^2} = \frac{a x+b}{x^2}. See how we're getting closer? With the common denominator in place, adding the fractions on the left side is a piece of cake. We just add the numerators and keep that common denominator. So, 3xx2+5x2\frac{3x}{x^2} + \frac{5}{x^2} becomes 3x+5x2\frac{3x+5}{x^2}. Now our equation is 3x+5x2=ax+bx2\frac{3x+5}{x^2} = \frac{a x+b}{x^2}. Look at that! We've successfully combined the fractions on the left. The next step is all about comparing this result to the right side of the equation to figure out what 'a' and 'b' have to be. It's all about matching things up, folks!

The 'Aha!' Moment: Matching Numerators

Okay, guys, we've done the heavy lifting of combining those fractions. We've arrived at 3x+5x2=ax+bx2\frac{3x+5}{x^2} = \frac{a x+b}{x^2}. Now comes the moment of truth, the 'aha!' moment where we solve for our unknowns, 'a' and 'b'. Since the denominators on both sides of the equation are identical (x2x^2), for the entire equation to be true, the numerators must also be equal. This is a fundamental rule in algebra: if two fractions with the same denominator are equal, then their numerators are also equal. So, we can simply equate the numerators: 3x+5=ax+b3x+5 = ax+b. Now, this is where we play the matching game. We have an expression on the left (3x+53x+5) and an expression on the right (ax+bax+b), and they are identical. We need to find the values of 'a' and 'b' that make these two expressions the same for all possible values of xx (except x=0x=0, of course, because we can't divide by zero!). Let's look at the terms involving xx first. On the left, we have 3x3x. On the right, we have axax. For these to be equal, the coefficients of xx must match. Therefore, aa must be equal to 33. Simple as that! Now, let's look at the constant terms (the numbers without any xx attached). On the left, we have the constant term +5+5. On the right, we have the constant term +b+b. For these to be equal, bb must be equal to 55. So, we've found our values: a=3a=3 and b=5b=5. It's like finding the keys that unlock the equation! This method relies on the principle of equating coefficients, where we match the coefficients of corresponding terms in two equal polynomials. It's a powerful technique for solving equations where you have unknown constants. So, the values that complete the sum are a=3a=3 and b=5b=5. Boom! Case closed.

Final Check: Does it All Add Up?

So, we've declared our answers: a=3a=3 and b=5b=5. But in the world of mathematics, especially when you're figuring stuff out, it's always, always a good idea to do a quick check to make sure your answers are spot on. It's like double-checking your work before handing in a big project – better safe than sorry, right? Let's plug our found values of aa and bb back into the original equation and see if everything balances out. Our original equation was 3x+5x2=ax+bx2\frac{3}{x}+\frac{5}{x^2}=\frac{a x+b}{x^2}. We found a=3a=3 and b=5b=5. So, let's substitute these into the right side: ax+bx2\frac{a x+b}{x^2} becomes 3x+5x2\frac{3 x+5}{x^2}. Now, let's look at the left side again. We started by combining 3x\frac{3}{x} and 5x2\frac{5}{x^2}. To do this, we found a common denominator, which was x2x^2. We rewrote 3x\frac{3}{x} as 3xx2\frac{3x}{x^2}. Then we added: 3xx2+5x2=3x+5x2\frac{3x}{x^2} + \frac{5}{x^2} = \frac{3x+5}{x^2}. Aha! Look at that! The left side, after combining the fractions, is 3x+5x2\frac{3x+5}{x^2}, and the right side, after plugging in our values for aa and bb, is also 3x+5x2\frac{3x+5}{x^2}. They are identical! This confirms that our values for aa and bb are indeed correct. This verification process is super important. It not only confirms your answer but also reinforces your understanding of how the algebraic manipulations work. If we had gotten a different result on the right side after plugging in our values, we'd know we needed to go back and re-examine our steps. But in this case, everything aligns perfectly. So, the values a=3a=3 and b=5b=5 are the correct ones that complete the sum as required. Great job, everyone, for working through this problem! Keep practicing these skills, and you'll be a fraction-combining pro in no time!