Question

Tính giá trị biểu thức A=3x^2-yz-xy+3xz tại x=2,3;y=3,9 và z=1,7

Answer 1

\(A=3x^2-yz-xy+3xz=3x\left(x+z\right)-y\left(x+z\right)\)

\(=\left(x+z\right)\left(3x-y\right)\)

Thay x,y,z

\(A=\left(x+z\right)\left(3x-y\right)=\left(2,3+1,7\right)\left(3.2,3-3,9\right)\)

\(=4.3=12\)

Answer 2

\(A=3x^2+3xz-yz-xy\)

\(=3x\left(x+z\right)-y\left(x+z\right)\)

\(=\left(x+z\right)\left(3x-y\right)\)

\(=4\cdot\left(3\cdot2.3-3.9\right)\)

\(=4\cdot3=12\)