Question

Find the factors of $x^2+18x+80$ by splitting the middle term.

• A. $(x+10)(x+8)$
• B. $(x+11)(x+8)$
• C. $(x+10)(x+10)$
• D. $(x+9)(x+8)$

Answer 1

The correct option is A

$(x+10)(x+8)$

Consider the constant 80.

We need to find two numbers such that product = 80 and sum= coefficient of middle term =18 .

10 and 8 are such numbers.

Write the middle term 18x using 10 and 8 as 18x= 10x+8x

$x^2+18x+80$

= $x^2+10x+8x+80$

= $x(x+10)+8(x+10)$

= $(x+10)(x+8)$