Problem: If the (convex) area bounded by the x-axis and the lines y=mx+4,x=1, and x=4 is 7, then m equals:
Answer Choices:
A. −1/2
B. −2/3
C. −3/2
D. −2
E. none of these
Solution:
The area of the trapezoid thus formed is 21(3)(m+4+4 m+4)=7.∴5 m=−310, m=−32.