ITMC 2026 Grade 8 National Preliminary sample-r1 Question 1

Question 1

Printed positive marks are preserved per question. The source uses different blank-answer and incorrect-answer rules by section, including an optional bonus penalty; the import does not reproduce that complete official scoring scheme.

Which identity is incorrect?

$(-x+2)^2=x^2-4x+4$
$(2x-y)^3=8x^3-12x^2y+6xy^2-y^3$
$x^3-8y^3=(x-2y)(x^2-2xy+4y^2)$
$x^2-100=(x+10)(x-10)$
$(x+1)^3=x^3+3x^2+3x+1$