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# need help

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Write down the quadratic equation whose roots are x = -7 and x = 8 and the coefficient of x^2 is 1.

Enter your answer in the form "x^2 + bx + c = 0".

Jul 3, 2021

#1
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$$x^2+x-56=0$$

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Jul 3, 2021
edited by Guest  Jul 3, 2021
#2
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that is just a little off.

x^2 + bx + c = 0

we know that one solution is -7, and the other one is 8

that means:

$\left. \begin{array} \ x=-7 \\ x=8 \end{array} \right\} \implies \left. \begin{array} \ x+7=0 \\ x-8=0 \end{array} \right\}$    knowing that we can write the quadratic as a factorised form$(x+7)(x-8)$

$(x+7)(x-8) \overset{\left(m+n\right)\left(p-q\right) = mp-mq+np-nq }{=============\Rightarrow} xx+x\left(-8\right)+7x+7\left(-8\right)$

$xx-8x+7x-7\cdot \:8$

$\boxed{ x^2-x-56 }$

Jul 3, 2021