the value of expression 2a^2+2b^2 - ab for a = 2, b = 1 is
Answers
Answer:
You can say in 5 seconds that answer is 1. In an objective exam; you will have four options like the value of given function is A. 1, B. 0, C.1/2, D. 2; even if the four options are in terms of a, b, c then put the value of a,b, c in options to eliminate wrong answers. Chances are high that you’ll eliminate all the wrong options.
Never solve it by traditional method in an objective exam as that’s a terrible waste of time and you’ll end up missing other questions. It’s about quickly solving questions; not your ability to solve it in 5 minutes.
Pick the most convenient value of a, b,c that satisfies a + b + c= 0
I will pick a=1, b==0, c= -1
On using these values, the function boils down to 1/2 + 0 + 1/2 = 1
There are 3 unknown and only one equation a + b+ c =0; when you solve these types of questions; everything cancels out and you get a definite answer; which is independent of the value of a, b, c;
I run “The Quants Blog” on Quora to share alternate way of answering quantitative aptitude questions. For solving this by traditional methods; please refer other answers given here.
Answer:
8
Step-by-step explanation:
a=2,b=1
a^2=4, b^2=1 , ab= 2
= 2(4)+2(1)-2
=8+2-2
=8