Giá trị của biểu thức A = x(2x + 3) - 4(x + 1) - 2x(x - 1/2) là?
2 câu trả lời
$A=x\left(2x+3\right)-4\left(x+1\right)-2x\left(\frac{x-1}{2}\right)$
$=x\left(2x+3\right)-4\left(x+1\right)-2x\frac{x-1}{2}$
$=x\left(2x+3\right)-4\left(x+1\right)-x\left(x-1\right)$
$=2x^2+3x-4\left(x+1\right)-x\left(x-1\right)$
$=2x^2+3x-4x-4-x\left(x-1\right)$
$=2x^2+3x-4x-4-x^2+x$
$=2x^2-x^2+3x-4x+x-4$
$=x^2+3x-4x+x-4$
$=x^2-4$
Answer
`A = x . (2x + 3) - 4 . (x + 1) - 2x . (x - 1/2)`
`A = x . 2x + x . 3 - 4 . x - 4 . 1 - 2x . x + 2x . 1/2`
`A = 2x^2 + 3x - 4x - 4 - 2x^2 + x`
`A = (2x^2 - 2x^2) + (3x - 4x + x) - 4`
`A = (-x + x) - 4`
`A = -4`
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