The factoring method is quite commonly used to easily find the real roots of a quadratic equation 2 things to know before doing this is Firstly, when we have (x−a)(x−b) , we set the other side to 0, because we want the x values where y is 0, so we have (x-a)(x-b) =0. And because of this, we separate it into two equations, where x-a=0 and x-b=0, so at the end, positive a and positive b are the x-intercepts. Secondly, the FOIL method used to check. FOIL method: forward, outside, inside, last (a+b)(c+d) = ac +ad + bc + bd (usually we are able to combine ad and bc) And how do we get to factored form from standard form? Well, let’s first take an example: x2+7x+6 In this, from seeing x^2, we know that we can set it to (x +/- _)(x +/- _) And now we want to set the signs, we can set this one right when we see the equation in this example, because both b and c are positive integers (in ax^2 + bx + c) So we can write (x+_)(x+_) Nowe we have to fill in the two blanks. We look at the c value, and see that it is 6, from this, we can list out all the factors that multiply to 6, and then find which pair adds up to 7 So we would have: 1 & 6 -> 1+6 = 7 2 & 3 -> 2+3=5 So, from above, we can see that the two blanks we are about to fit in are 1 and 6. So we have (x+6)(x+1) and you can also check this by using the FOIL method Check: (x+6)(x+1) = x^2 + x + 6x + 6 = x^2 + 6x + 6 So we are correct And from (x+6)(x+1) we can determine that -6 and -1 are the roots, and so the coordinates are (-6,0) and (-1,0) And so now, we can move on to the next scenario, if we had, for example x2−7x+6 As you can see, I’m using the same numbers, just changing b into a negative integer From this, we know that we need to integers that multiply up to 6, but add up to -7, in these kind of cases, it is obvious that the two signs in the the expression are both negative, because negative and negative makes positive, which gets our c value to be a positive integer, but also gets our b value to a negative number since -x+(-y) = -x-y, so it is negative So we can set this up to (x-_)(x-_) From here, we can see that again, 1 times 6 is six, and adds up to 7, so we have (x−6)(x−1) And again, we can check using the FOIL method Check: (x-6)(x-1) = x^2 -x - 6x + 6 = x^2 -7x + 6 And from (x-6)(x-1) we can determine that 6 and 1 are the roots, so the coordinates are (6,0) and (1,0) The next scenario is where one sign is positive, the other is negative For example, if we had x2+2x−15
\[thetannhdd21312\]
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