Question

B.1 Tính giá trị biểu thức

a) A = 3x³y + 6x²y² + 3xy³ tại x = 1/2, y = -1/3

b) B = x²y² + xy + x³ + y³ tại x = -1, y = 3

B. 2: Cho đa thức:

P(x) = x⁴ + 2x² + 1, Q(x) = x⁴ + 4x³ + 2x² - 4x + 1

Tính: P(-1), P(1/2), Q(-2), Q(1)

Answer 1

B.1:

a) Với x = 1/2, y = -1/3, A= \(3\left(\frac{1}{2}\right)^3\left(-\frac{1}{3}\right)+6\left(\frac{1}{2}\right)^2\left(-\frac{1}{3}\right)^2+3.\frac{1}{2}.\left(-\frac{1}{3}\right)^3\)=\(\frac{-1}{8}+\frac{1}{6}+\frac{-1}{18}\)=\(\frac{-1}{72}\)

b)Với x = -1, y = 3, B=

\(\left(-1\right)^2.3^2+\left(-1\right).3+\left(-1\right)^3+3^3\)\(=9+\left(-3\right)+\left(-1\right)+27\)

\(=32\)

B.2:

\(P\left(-1\right)=\left(-1\right)^4+2.\left(-1\right)^2+1\)\(=1+2+1=4\)

\(P\left(\frac{1}{2}\right)=\left(\frac{1}{2}\right)^4+2.\left(\frac{1}{2}\right)^2+1\)\(=\frac{1}{16}+\frac{1}{2}+1\)\(=\frac{25}{16}\)

\(Q\left(-2\right)=\left(-2\right)^4+4\left(-2\right)^3+2\left(-2\right)^2-4\left(-2\right)+1\)\(=16+\left(-32\right)+8-\left(-8\right)+1=1\)

\(Q\left(1\right)=1^4+4.1^3+2.1^2=1+4+2=7\)

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