Please enter the following details
Free Daily Targets & Mocks
Study Material & Formulas PDFs
1 on 1 Mentorship
Solution
Given : $$(a-b)=1$$ and $$(a^3-b^3)=61$$
We know that, $$(a^3-b^3)=(a-b)(a^2+b^2+ab)$$
=> $$61=1(a^2+b^2+ab)$$
=> $$a^2+^2+ab=61$$
=> $$a^2+b^2=61-ab$$ ----------(i)
Also, $$(a-b)^2=a^2+b^2-2ab$$
Substituting value from equation (i)
=> $$(1)^2=(61-ab)-2ab$$
=> $$1=61-3ab$$
=> $$3ab=61-1=60$$
=> $$ab=\frac{60}{3}=20$$
=> Ans - (B)
Create a FREE account and get:
- Free SSC Study Material - 18000 Questions
- 230+ SSC previous papers with solutions PDF
- 100+ SSC Online Tests for Free
