Question

solve x^2−10x=−21x

Quadratic function and equation
ANSWERED
asked 2020-10-21
solve \(\displaystyle{x}^{{2}}−{10}{x}=−{21}{x}\)

Answers (2)

2020-10-22
We have to solve: solve x2−10x=−21
\(\displaystyle{x}^{{2}}-{10}{x}=-{21}\to{x}^{{2}}-{10}{x}+{21}={0}\)
For a quadratic equation of the form \(\displaystyle{a}{x}^{{2}}+{b}{x}+{c}={0}\) the solution are \(\displaystyle\frac{{-{b}\pm\sqrt{{{b}^{{2}}-{4}{a}{c}}}}}{{2}}{a}\)
Therefore the solution of the given equation are \(\displaystyle\frac{{-{\left({10}\right)}\pm\sqrt{{{\left(-{10}\right)}^{{2}}}}-{4}\cdot{1}\cdot{21}}}{{2}}\cdot{1}=\frac{{{10}+\sqrt{{16}}}}{{2}}\cdot{1}=\frac{{{10}\pm{4}}}{{2}}={7.3}\)
Hence the solution are x=7 and x=3
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2021-08-10

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