Toán P = 5x(x2 – 3) + x2(7 – 5x) – 7×2 với x = – 5 31/08/2021 By Kylie P = 5x(x2 – 3) + x2(7 – 5x) – 7×2 với x = – 5
$P(x)=5x(x^2-3)+x^2(7-5x)-7x^2$ $= 5x^3-15x+7x^2-5x^3-7x^2$ $= -15x$ $\Rightarrow P(-5)=-15.(-5)=75$ Trả lời
`P=5x(x^2-3)+x^2(7-5x)-7x^2`
`⇔P=5x^3-15x+7x^2-5x^3-7x^2`
`⇔P=-15x`
`⇔P=-15.(-5)`
`⇔P=75`
$P(x)=5x(x^2-3)+x^2(7-5x)-7x^2$
$= 5x^3-15x+7x^2-5x^3-7x^2$
$= -15x$
$\Rightarrow P(-5)=-15.(-5)=75$