Question

用两种方法解二元一次方程组,分别是代入法和加减法.？

Answer 1

(1) 3x + 2(1-x) = 5 ==> x = 3, y = -2
① - 2*② ==> x = 3, y = -2
(2) 3x + 5(2x - 1) = 8 ==> x = 1, y = 1
① + 5*② ==> x = 1, y =1
(3) x + 3(2x - 25) = 30 ==> x = 15, y = 5
2*① - ② ==> y = 5, x = 15
(4) 3x - 4(x/2 - 2/3) = 7 ==> x = 13/3, y = 3/2
6*① - ② ==> y = 3/2, x = 13/3,3,第四题答案错，应是x=3，y=1/2.重新计算哈！,用两种方法解二元一次方程组咐嫌,分别宴简渣是代入法和加减法晌悄.
（1）3x+2y=5,①y=1-x.② （2）3x+5y=8,①2x-y=1.② （3） x+3y=30,①2x-y=25； ⑶ x/2-y+1/3=1①3x-4y=7②