Evaluate
\text{Indeterminate}
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\frac{-12\left(7+\sqrt{-1}\right)}{\left(7-\sqrt{-1}\right)\left(7+\sqrt{-1}\right)}
Rationalize the denominator of \frac{-12}{7-\sqrt{-1}} by multiplying numerator and denominator by 7+\sqrt{-1}.
\frac{-12\left(7+\sqrt{-1}\right)}{7^{2}-\left(\sqrt{-1}\right)^{2}}
Consider \left(7-\sqrt{-1}\right)\left(7+\sqrt{-1}\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}.
\frac{-12\left(7+\sqrt{-1}\right)}{49+1}
Square 7. Square \sqrt{-1}.
\frac{-12\left(7+\sqrt{-1}\right)}{50}
Subtract -1 from 49 to get 50.
-\frac{6}{25}\left(7+\sqrt{-1}\right)
Divide -12\left(7+\sqrt{-1}\right) by 50 to get -\frac{6}{25}\left(7+\sqrt{-1}\right).
-\frac{6}{25}\times 7-\frac{6}{25}\sqrt{-1}
Use the distributive property to multiply -\frac{6}{25} by 7+\sqrt{-1}.
\frac{-6\times 7}{25}-\frac{6}{25}\sqrt{-1}
Express -\frac{6}{25}\times 7 as a single fraction.
\frac{-42}{25}-\frac{6}{25}\sqrt{-1}
Multiply -6 and 7 to get -42.
-\frac{42}{25}-\frac{6}{25}\sqrt{-1}
Fraction \frac{-42}{25} can be rewritten as -\frac{42}{25} by extracting the negative sign.
Examples
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y = 3x + 4
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Matrix
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Simultaneous equation
\left. \begin{cases} { 8x+2y = 46 } \\ { 7x+3y = 47 } \end{cases} \right.
Differentiation
\frac { d } { d x } \frac { ( 3 x ^ { 2 } - 2 ) } { ( x - 5 ) }
Integration
\int _ { 0 } ^ { 1 } x e ^ { - x ^ { 2 } } d x
Limits
\lim _{x \rightarrow-3} \frac{x^{2}-9}{x^{2}+2 x-3}