\[{a}^{2}-10.5a-25=0\]

1
Factor with quadratic formula.
(a252)(a+2)=0(a-\frac{25}{2})(a+2)=0

2
Solve for aa.
a=252,2a=\frac{25}{2},-2

Done

Decimal Form: 12.5, -2

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