Question

 A = (4x – 7,5) + x:3 khi x = -2,1

Answer 1

\(A=\left(-2.1\cdot4-7.5\right)+\left(-2.1\right):3=-15.9-6.3=-22.2\)

Answer 2

Thay x=-2,1 vào A ta có:
\(A=\left(4x-7,5\right)+x:3\\ \Rightarrow A=\left[4.\left(-2,1\right)-7,5\right]-2,1:3\\ \Rightarrow A=\left(-8,4-7,5\right)-0,7\\ \Rightarrow A=\left(-15,9\right)-0,7\\ \Rightarrow A=-16,6\)