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.

Question

anonymous · Answer

put 
$$x^2+4x-5=7$$ and solve for x via 
$$x^2+4x-12=0$$
$$(x+6)(x-2)=0$$
$$x+6=0$$
$$x=-6$$
$$x-2=0$$
$$x=2$$ and in this problem the negative answer makes no sense so it is just x = 2

jhonyy9 · Answer

x*2 +4x -5 = 7*2 --- x*2 +4x -5 =49 --- x*2 +4x  -54 =0
              4 +/- (16 + 216)*(1/2)       4 +/- (232)*(1/2)       2(2+/- (58)*(1/2)
x_1,_2 = --------------------- = ----------------- = ---------------- =
                            2                                       2                                 2

=2+/- (58)*(1/2)

x_1,_2 = 2+/- radical 58