Question

[tex] Find x ∈ R if A=\left[\begin{array}{ccc}5x&10\\8&7\end{array}\right] and | A |=25. [\tex]

Answer 1

Answer:

$x = 3$

Step-by-step explanation:

Given that

| A |=25

$A=\left[\begin{array}{ccc}5x&10\\8&7\end{array}\right]$

So determinant A

$|A| = 35x - 80$

But it is given that |A|= 25

So equate both

$35x - 80 = 25 \\ \\ 35x = 25 + 80 \\ \\ 35x = 105 \\ \\ x = \frac{105}{35} \\ \\ x = 3$

So

$x = 3 \: \: \: \: \epsilon \: R$

Hope it helps you.