The value of the algebraic formula - 10x + 7x-4 is always less than 0

The value of the algebraic formula - 10x + 7x-4 is always less than 0

-10x + 7x-4 = - 10 [X-2 * 7 / 20 + (7 / 20) - (7 / 20) + 4 / 10] = - 10 [(X-7 / 20) - 49 / 400 + 160 / 400] = - 10 [(X-7 / 20) + 111 / 400] because (X-7 / 20) ≥ 0, so (X-7 / 20) + 111 / 400 > 0 is constant in the real range, so - 10x + 7x-4 = - 10 [(X-7 / 20) + 111 / 400] < 0 is constant