Digital ACT Math Practice Question #1206
Test your problem-solving accuracy on this official-caliber item. Select an answer choice to check your reasoning instantly.
Test Choice A ($x = 5$): $\det = 5(4) - 3(4) = 20 - 12 = 8$. Match found on the first try!
The determinant of a $2 \times 2$ matrix $\begin{bmatrix} a & b \\ c & d \end{bmatrix}$ is $ad - bc$. $$\det(M) = x(x - 1) - (3)(4) = x^2 - x - 12.$$ Set the determinant equal to $8$: $$x^2 - x - 12 = 8 \implies x^2 - x - 20 = 0.$$ Factorin...
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