求过点M(-2,1)和点N(2,9)的直线方程
y = ax + b;代入坐标
-2a + b = 1,2a + b = 9;
两式相减,4a = 8,a = 2;
2 * 2 + b = 9,b = 5;
直线方程是 y = 2x + 5 。
(y-1)/(9-1)=[x-(-2)]/[2-(-2)]
(y-1)/8=(x+2)/4
y-1=2(x+2)
y=2x+5
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y = ax + b;代入坐标
-2a + b = 1,2a + b = 9;
两式相减,4a = 8,a = 2;
2 * 2 + b = 9,b = 5;
直线方程是 y = 2x + 5 。
(y-1)/(9-1)=[x-(-2)]/[2-(-2)]
(y-1)/8=(x+2)/4
y-1=2(x+2)
y=2x+5