Bài 1:A=4x4+7x2y2+3y4+5y2=4x2(x2+y2)+3y2(x2+y2)+5y2=20x2+15y2+5y2=20(x2+y2)=100.

A=4x⁴+7x²y²+3y⁴+5y²

=4x²(x²+y²)+3y²(x²+y²)+5y²

=20x²+15y²+5y² 

=20x²+(15+5)y²

=20(x²+y²)=100

A = 4x⁴ + 7x²y² + 3y⁴ + 5y²

= 4x⁴ + 4x²y² + 3x²y² + 3y⁴ + 5y²

= 4x²(x² + y²) + 3y²(x² + y²) + 5y²

= 4x² . 5 + 3y² . 5 + 5y²

= 20x² + 15y² + 5y²

= 20x² + 20y²

= 20(x² + y²)

= 20 . 5 

= 100

 Thái Viết Nam 

Với x² + y² = 5

Ta có:

A = 4x⁴ + 7x² y²  + 3y⁴ + 5y²

    = 4x⁴  + 4x² y²  + 3x² y² + 5y² 

  = 4x² . ( x² + y² ) + 3y2 . ( x² + y² ) + 5y² 

= 4x²  . 5 + 3y²  . 5 + 5y² 

= 20x² + 15y²  + 5y²  

= 20x²  20y² = 20. ( x² + y² ) = 20 . 5 = 100

Vậy A = 100 

^^ Học tốt! 

A=4x⁴+7x²y²+3y⁴+5y²=(4x⁴+8x²y²+4y⁴)-x²y²-y⁴+5y²=(2x²+2y²)²-y²(x²+y²)+5y²=4(x²+y²)²-y²(x²+y²)+5y²

Thay x²+y²=5 vào A, Ta được:

A=4*5²-y²*5+5*y²=4*25=100

Vậy A=100

\(A=4x^4+7x^2y^2+3y^4+5y^2=\left(4x^4+4x^2y^2\right)+\left(3x^2y^2+3y^4\right)+5y^2\)

\(=4x^2\left(x^2+y^2\right)+3y^2\left(x^2+y^2\right)+5y^2=20x^2+20y^2\)

\(=20\left(x^2+y^2\right)=20.5=100\)

P = 4x⁴ + 7x²y² + 3y⁴ + 5y² 

= (4x⁴ + 4x²y²) + (3x²y² + 3y⁴) + 5y²

= 4x²(x² + y²) + 3y²(x² + y²) + 5y²

= (4x² + 3y²)(x² + y²) + 5y²

= (4x² + 3y²).5 + 5y² (Vì x² + y² = 5)

= 5(4x² + 3y² + y²)

= 5(4x² + 4y²)

= 5.4.(x² + y²) = 5.4.5 = 100

Ta có: M=4x⁴+7x²y²+3y⁴+5y²

=>M=4x⁴+4x²y²+3x²y²+3y⁴+5y²

=>M=(4x⁴+4x²y²)+(3x²y²+3y⁴)+5y²

=>M=4x².(x²+y²)+3y².(x²+y²)+5y²

Vì x²+y²=5

=>M=4x².5+3y².5+5y²

=>M=20x²+15y²​+5y²

=>M=20x²+20y²

=>M=20.(x²+y²)

=>M=20.5

=>M=100

Vậy M=100