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Answers for “找到 x=2 后,为什么讲师代入原始方程而不是化简后的系统?”

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The two equations can be added directly to eliminate yy because their yy-coefficients are exact opposites (−4y-4y and +4y+4y). When equations with opposite coefficients for the same variable are added term by term, those terms cancel out to zero, leaving a one-variable equation in xx.

Conditions: The system has been reduced to integer coefficients: 3x−4y=143x - 4y = 14 and 15x+4y=2215x + 4y = 22.; The equations are aligned term-by-term before addition.

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The equation is multiplied by 3 to clear the denominators and eliminate the fractions. Since the denominators present are 1 and 3, the common denominator is 3.

Conditions: The equation contains fractional terms with denominators 1 and 3.; All terms on both sides of the equation are multiplied by the same nonzero number (3).