Question

${x}^{2} + 21 = 10 \times$
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Answer 1

${x}^{2} + 21 = 10x \\ {x}^{2} - 10x + 21 = 0 \\ x_{1} + x_{2} = 10 \\ x_{1} \times x_{2} = 21 \\ x_{1} = 3 \\ x_{2} = 7$