Q9
In the xy-plane, if line k passes through the points
(3.-4) and (a,b), where b=4a-16 and a≠3,
what is the slope of k?
A. –4
B. –1/2
C. 0
D. 2
E. 4
找不到讨论,不好意思请问各位NN,这题怎么考虑呀,谢谢!
两种做法都可以:
1.非常规快速做法: 由于(a,b)在直线上,又说b=4a-16, 所以你就可以猜直线是y=4x-16了,把(3,-4)代入发现果然正确。所以斜率k=4
2.常规做法:根据点斜式设直线方程为 Y+4 = k(x-3) (k为斜率), 把(a,4a-16)代入直线然后化简可得: (4-k)a = 3(4-k);若4-k不等于0,可得a=3,但题目说a不等于3,所以4-k必为0,得k=4
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