The area of a rectangle is given by A = x2 + 4x – 5. Find the value of x if the total area of the rectangle is equal to 7 square units.

a) x = 1
b) x = 7
c) x = 2
d) x = 5

Question

The area of a rectangle is given by A = x2 + 4x – 5. Find the value of x if the total area of the rectangle is equal to 7 square units.

a)  x = 1 
 b)  x = 7 
 c) x = 2 
 d) x = 5

anonymous · Answer

c

radar · Answer

$$7=x ^{2}+4x-5$$
$$x ^{2}+4x-12=0$$factoring would be the way to go!
(x+6)(x-2)=0       If this product equals zero then one (or both) equals zero
x+6=0  giving x=-6  not a good answer as dimensions are positive
x-2=0   giving x=2    That is a good solution.  But better check   and verify!
$$7=2^{2}+4(2)-5$$$$7=4+8-5=7$$  Final answer x=2