Question:
Factorise:
28 − 31x − 5x2
Solution:
The given expression is $28-31 x-5 x^{2}$.
Find two numbers that follow the conditions given below:
Sum $=-31$
Product $=28 \times-5=-140$
Clearly, the numbers are $-35$ and 4 .
$28-31 x-5 x^{2}=28+4 x-35 x-5 x^{2}$
$=4(x+7)-5 x(7+x)$
$=(x+7)(4-5 x)$
Click here to get exam-ready with eSaral
For making your preparation journey smoother of JEE, NEET and Class 8 to 10, grab our app now.