Expand the product $(2 x + 3) (4 x - 5)$ .

easy 1 mark Class 7 · Mathematics · Algebraic Expressions

Answer

8x^2 + 2x - 15

The correct answer is 8x^2 + 2x - 15 — Combine like terms $- 10 x + 12 x = 2 x$ and add the constant $- 15$ .

Step-by-step solution

Multiply $2 x$ with each term of the second parenthesis: $2 x c d o t 4 x = 8 x^{2}$ , $2 x c d o t (- 5) = - 10 x$ .
Multiply $3$ with each term of the second parenthesis: $3 c d o t 4 x = 12 x$ , $3 c d o t (- 5) = - 15$ .
Combine like terms $- 10 x + 12 x = 2 x$ and add the constant $- 15$ .

Common mistake: Forgetting to distribute the negative sign

Concept tested: Expansion of binomials