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Mathematics 9 Online
OpenStudy (anonymous):

x^2-4x+14=49

OpenStudy (anonymous):

ok so i think i have the concept on what to do next can you tell me if its right or wrong

OpenStudy (anonymous):

\[x^2-4x-49=0\]

OpenStudy (hba):

Subtract both sides by 49

OpenStudy (anonymous):

it started out as.....

OpenStudy (anonymous):

\[x^2-4x+4=49\]

OpenStudy (anonymous):

i then subtracted 49 from both sides to have it set = to 0 is that right

OpenStudy (hba):

No it is x^2-4x+14=49 Now you subtract both sides by 49

OpenStudy (anonymous):

im sorry that was a typo the equation started as x^2-4x+4=49

OpenStudy (anonymous):

so whats next combining the like terms??

OpenStudy (hba):

Subtracting both sides by 49 What do you get ?

OpenStudy (hba):

x^2-4x+4-49=49-49

OpenStudy (anonymous):

you would get x^2-4x-45=0

OpenStudy (anonymous):

x^2-4x+14=49 x^2-4x=49-14 x^2-4x=35 x(x-4_=35 x=35 or x-4=35 x=39

OpenStudy (anonymous):

line 4 edit: x(x-4)=35

OpenStudy (anonymous):

@aleksas1234 That's not correct. Insert x = 39 into the equation, you'll see that it won't hold. Furthermore, you'll always get 2 solutions from a quadratic equation. Thats's proven, it's called the Fundamental Theorem of Algebra.

OpenStudy (anonymous):

So, for the solution, lets start off at \[x^2 - 4x - 45 = 0\]There are 2 ways to solve this. Have you heard of the solution formula for quadratic equations or linear factorization of polynomials?

OpenStudy (anonymous):

@Stiwan owh i found my mistace, ty

OpenStudy (anonymous):

For any quadratic equation of the form\[x²+px + q = 0 \] holds that \[x_1 = - \frac{p}{2} + \sqrt{(\frac{p}{2})^2 - q}\]\[x_2 = -\frac{p}{2} - \sqrt{(\frac{p}{2})^2 - q}\] Where x_1, x_2 are the zeroes of the equation above. By plugging in p = -4 and q = -5 You get x_1 = 9, x_2 = -5

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