(1)若Ia-3I+Ib-4I=0,求a和b的值 (2) 若Ia+1I+Ib-1/2I=0,求2ab的值

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(1)若Ia-3I+Ib-4I=0,求a和b的值 (2) 若Ia+1I+Ib-1/2I=0,求2ab的值

(1)若Ia-3I+Ib-4I=0,求a和b的值 (2) 若Ia+1I+Ib-1/2I=0,求2ab的值
(1)若Ia-3I+Ib-4I=0,求a和b的值 (2) 若Ia+1I+Ib-1/2I=0,求2ab的值

(1)若Ia-3I+Ib-4I=0,求a和b的值 (2) 若Ia+1I+Ib-1/2I=0,求2ab的值
(1)∵Ia-3I+Ib-4I=0
∴a-3=0 b-4=0
∴a=3,b=4

(2)∵Ia+1I+Ib-1/2I=0
∴a+1=0,b-1/2=0
∴a=-1 b=1/2
∴2ab=2*(-1)*1/2=-1/2

(1)由条件可知|a-3|=0,|b-4|=0,所以a=3,b=4
(2)由条件知|a+1|=0,|b-1/2|=0,得a=-1,b=1,所以2ab=-2

<1> a=3 b=4
<2> a=-1 b=1/2 2ab=-1