Question:
Factorise:
2x2 + x − 45
Solution:
The given expression is $2 x^{2}+x-45$.
Find two numbers that follow the conditions given below:
Sum $=1$
Product $=-45 \times 2=-90$
Clearly, the numbers are 10 and $-9$.
$2 x^{2}+x-45=2 x^{2}+10 x-9 x-45$
$=2 x(x+5)-9(x+5)$
$=(2 x-9)(x+5)$
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