1. To know m-2n = - 2, find the value of - 3-2m + 4N 2. Such a question, "a = 2A & sup2; + 2B & sup2; - 3C & sup2;, B = 3A & sup2; - B & sup2; - 2C & sup2;, C = C & sup2; + 2A & sup2; - 3B & sup2;, when a = 1, B = 2, C = 3, find the value of A-B + C". One student pointed out that the B = 2, C = 3 given in the question is redundant. Is his saying reasonable? Why? | Math enthusiast | Mathematical art

1. To know m-2n = - 2, find the value of - 3-2m + 4N 2. Such a question, "a = 2A & sup2; + 2B & sup2; - 3C & sup2;, B = 3A & sup2; - B & sup2; - 2C & sup2;, C = C & sup2; + 2A & sup2; - 3B & sup2;, when a = 1, B = 2, C = 3, find the value of A-B + C". One student pointed out that the B = 2, C = 3 given in the question is redundant. Is his saying reasonable? Why?

solution
1,-3-2m+4n=-3-（2m-4n）=-3+4=1
2,A-B+C=2a²+2b²-3c²-(3a²-b²-2c²)+c²+2a²-3b²
=2a²+2b²-3c²-3a²+b²+2c²+c²+2a²-3b²
=a²
So it doesn't contain terms B and C, so it's right
Adopt

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