已知a=(3,-5),b=(9,11),c=(8,13),求:
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已知a=(3,-5),b=(9,11),c=(8,13),求:
(1) -2a+3b-4c
(2) 15a-6b+7c
(1) -2a+3b-4c
(2) 15a-6b+7c
![已知a=(3,-5),b=(9,11),c=(8,13),求:](/uploads/image/z/19777805-53-5.jpg?t=%E5%B7%B2%E7%9F%A5a%3D%283%2C-5%29%2Cb%3D%289%2C11%29%2Cc%3D%288%2C13%29%2C%E6%B1%82%EF%BC%9A)
因为a=(3,-5),b=(9,11),c=(8,13),
所以:
(1) -2a+3b-4c
=(-6,10)+(27,33)-(32,52)
=(-6+27-32,10+33-52)
=(-11,-9)
(2) 15a-6b+7c
=(45,-75)-(54,66)+(56,91)
=(45-54+56,-75-66+91)
=(47,-50)
所以:
(1) -2a+3b-4c
=(-6,10)+(27,33)-(32,52)
=(-6+27-32,10+33-52)
=(-11,-9)
(2) 15a-6b+7c
=(45,-75)-(54,66)+(56,91)
=(45-54+56,-75-66+91)
=(47,-50)
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