a的二次方+2a-14=0,则(a-3)(a+6)(a+5)(a-4)+20的值是
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a的二次方+2a-14=0,则(a-3)(a+6)(a+5)(a-4)+20的值是
a的二次方+2a-14=0,则(a-3)(a+6)(a+5)(a-4)+20的值是
a的二次方+2a-14=0,则(a-3)(a+6)(a+5)(a-4)+20的值是
a^2+2a-14=0
(a+1)^2=15
(a-3)(a+6)(a+5)(a-4)+20
=【(a+5)(a-3)】【(a+6)(a-4)】+20
=【(a+1+4)(a+1-4)】【(a+1+5)(a+1-5)】+20
=【(a+1)^2-16】【(a+1)^2-25】+20
=【15-16】【15-25】+20
=(-1)*(-10)+20
=10+20
=30
a方-2a+1-15=0
(a+1)方=15
设(a+1)=A,则A方=15
方程为(A-4)(A+5)(A+4)(A-5)+20=
(A方-16)(A-25)+20=-1*(-10)+20=30
没演算过,可参考
因为a^2+2a-14=0
所以(a+1)^2=15
(a-3)(a+6)(a+5)(a-4)+20
=【(a+5)(a-3)】【(a+6)(a-4)】+20
=【(a+1+4)(a+1-4)】【(a+1+5)(a+1-5)】+20
=【(a+1)^2-16】【(a+1)^2-25】+20
=【15-16】【15-25】+20
=(-1)*(-10)+20
=10+20
=30
a^2+2a-14=0
(a+1)^2=15
(a-3)(a+6)(a+5)(a-4)+20
=【(a+5)(a-3)】【(a+6)(a-4)】+20
=【(a+1+4)(a+1-4)】【(a+1+5)(a+1-5)】+20
=【(a+1)^2-16】【(a+1)^2-25】+20
=【15-16】【15-25】+20
=(-1)*(-10)+20
=10+20
=30