{3x+2y=-5 {4x-3y= -18

1 answer:

3 0

$\left\{\begin{array}{ccc}3x+2y=-5&|\cdot3\\4x-3y=-18&|\cdot2\end{array}\right\\\\\underline{+\left\{\begin{array}{ccc}9x+6y=-15\\8x-6y=-36\end{array}\right}\qquad\text{add both sides of the equations}\\\\.\qquad17x=-51\qquad|:17\\.\qquad x=-3\\\\\text{put the value of x to the first equation}\\\\3(-3)+2y=-5\\-9+2y=-5\qquad\text{add 9 to both sides}\\2y=4\qquad\text{divide both sides by 2}\\y=2\\\\Answer:\ \boxed{x=-3\ and\ y=2}$

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<u>Roots of a polynomial</u>

If we know the roots of a polynomial, say x1,x2,x3,...,xn, we can construct the polynomial using the formula

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Where a is an arbitrary constant.

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