Question

[Yến Chử]

khai triển các biểu thức sau:

\(a.\left(2x+3y\right)^2\)

\(b.2\left(\dfrac{1}{2}x^2+y\right)\left(x^2-2y\right)\)

\(c.\left(x+y+z\right)^2\)

Answer 1

[Toru]

a. (2x+3y)²= (2x)²+2.2x.3y+(3y)²

=4x²+12xy+9y²

b. 2(\(\dfrac{1}{2}\)x²+y)(x²-2y)

=(x²+2y)(x²-2y)

=x⁴-4y²

c, (x+y+z)²= [(x+y)+z]²

=(x+y)²+2(x+y)z+z²

=x²+2xy+y²+2xz+2yz+z²

=x²+y²+z²+2xy+2yz+2xz