Question

Find the third side of a triangle whose two sides are $(3x^2-5x)$ cm and $(4x^2+12)$ cm and perimeter is $(8x^2-9x+4)$ cm.

• A. $(x^2+4x-8)$ cm
• B. $(x^2-4x+8)$ cm
• C. $(x^2-4x-8)$ cm
• D. $(x^2+4x+8)$ cm

Answer 1

The correct option is C

$(x^2-4x-8)$ cm

Let the unknown side be $y$ cm.

Perimeter of the triangle = sum of its three sides

$⟹$ $8x^2-9x+4$ = $(3x^2-5x)$ + $(4x^2+12)$ +$y$

$⟹y=(8x^2-9x+4)-(3x^2-5x)-(4x^2+12)$

$⟹y=8x^2-9x+4-3x^2+5x-4x^2-12$

$⟹y=8x^2-4x^2-3x^2-9x+5x+4-12$

$⟹y=(x^2-4x-8)cm$