(1)(4a-1)()=16a^2-1(2)(2x+)(?-3y)=4x^2-9y^21.计算(1)(b-2)(b^2+4)(b=2)(2)-(5+2x)(5-2x)2.完全平方公式=?(1)(-2a+b)^2(2)(-2m-3n)^2(3)(69×1/2)^2(4)101^2+99^2(5)(a-2b+3c)(a-3c-2b)

Question

(1) (4a-1)( )=16a^2-1
(2) (2x+ )(?-3y)=4x^2-9y^2
1.计算
(1)(b-2)(b^2+4)(b=2)
(2)-(5+2x)(5-2x)
2.完全平方公式=?
(1)(-2a+b)^2
(2)(-2m-3n)^2
(3) (69×1/2)^2
(4) 101^2+99^2
(5)(a-2b+3c)(a-3c-2b)

Answer 1

(1) (4a-1)(4a+1)=16a^2-1
(2) (2x+3y)(2x-3y)=4x^2-9y^2
1.计算
(1)(b-2)(b^2+4)(b+2)
=(b-2)(b+2)(b^2+4)
=(b^2-4)(b^2+4)
=b^4-16
(2)-(5+2x)(5-2x)
=(2x+5)[-(5-2x)]
=(2x+5)(2x-5)
=4x^2-25
2.完全平方公式=?
(1)(-2a+b)^2=(-2a)^2+2*(-2a)*b+b^2=4a^2-4ab+b^2
(2)(-2m-3n)^2=[-1*(2m+3n)]^2=(-1)^2*(2m+3n)^2=4m^2+12mn+9n^2
(3) (69×1/2)^2=69^2×(1/4)=4761/4
(4) 101^2+99^2=(100+1)^2+(100-1)^2=100^2+200+1+100^2-200+1=20002
(5)(a-2b+3c)(a-3c-2b)
=[(a-2b)+3c][(a-2b)-3c]
=(a-2b)^2-9c^2
=a^2-4ab+4b^2-9c^2