Phân tích đa thức thành nhân tử a). 16-(3-x) mũ 2 b). (7x-4)mũ 2 -(2x+1) mũ 2 c). 49(y-4)mũ 2 -9(y+2)mũ 2

a ) $16$ - ( $3-x )^{2}$

= $4^{2}$ - ( $3-x )^{2}$

= ( 4 - 3 +x ) . ( 4+3-x )

= ( 1 + x). ( 7-x)

b) $(7x - 4 )^{2}$ - $(2x + 1 )^{2}$ 

= ( 7x - 4 - 2x - 1 ) . ( 7x - 4 +2x + 1 )

= ( 5x - 5 ) . ( 9x -3 ) 

c ) $49.(y-4)^{2}$ - $9.( y +2 )^{2}$ 

= $[7. ( y-4) ]^{2}$ - $[3. ( y+2)]^{2}$

= [ 7.( y-4) - 3.(y+2) ] . [ 7.( y-4) + 3.(y+2) ] 

= ( 7y - 28- 3y-6 ) . ( 7y - 28+3y + 6 )

= ( 4y - 34 ). ( 10y -22 )