Question

What is the length of line PS

Answer 1

$PQ^2 = PR \times PS$

$(4x + 4)^2 = (3x + 3)(3x + 3 + 21)$

$16x^2 + 32x + 16= (3x + 3)(3x + 24)$

$16x^2 + 32x + 16= 9x^2 + 81x + 72$

$7x^2 - 49x- 56 = 0$

$7(x^2 - 7x - 8)= 0$

$(x - 8)(x + 1) = 0$

$x - 8 = 0~~~or~~~x + 1 = 0$

$x = 8~~~or~~~x = -1$

x = -1 makes the lengths of segments PQ and PR equal zero.
That is not possible, so the solution x = -1 is discarded.

x = 8

PS = 3x + 3 + 21

PS = 3x + 24

PS = 3(8) + 24

PS = 24 + 24

PS = 48